River Cottage Love Your Leftovers

In my hierarchy of leftovers, fish rides high; in fact, it’s right at the top of the list. Given the preciousness of it as a resource, the perils of getting it to shore and the rightful expense of buying it, I don’t want to waste even a morsel.

For that reason, I have over the years developed ways of using every scrap of fish at my disposal. I start with (or more often, end with) the skeleton: heads and bones can, of course, be used in stocks and soups (see Fish head soup), but they can be stars of a dish too – see my spicy crispy skeletons.

Fish skin, meanwhile, carries so much flavour that I never toss it – I’ve even been known to collect it from people’s plates, after a meal, without the merest blush of shame. Roasted or fried, it transforms into fish skin ‘scratchings’, which make a great little snack or garnish for salads as well as a kind of piscine crispy ‘bacon’ for sandwiches.

Smoked fish has always been a favourite of mine. Its intensity of flavour is a highly desirable leftovers attribute: a small amount packs a lot of punch. That means you don’t need much – and, let’s face it, if you’re dealing with fishy leftovers, you probably won’t have a lot. In fact, I think of leftover smoked fish almost as a seasoning – its smokiness adding depth and savour to the whole, without being the star event in itself. Dishes like the smoky fish gratin illustrate just what I mean.

So keen am I on leftover fish and its myriad culinary uses, that it’s one of those ingredients I quite often cook as a ‘planned-over’, not least because it’s very much easier to part flesh from bone when it’s still warm than wait until the next day. So, if you have some fresh raw fish that needs using but you’re not sure what you want to do with it yet, get cracking and cook it.

Store properly after cooking (cool quickly, then keep in a sealed container in the fridge) to buy yourself an extra couple of days to decide upon some delicious use for it. Try flaking it onto salads, soups or blinis, folding it into tasty, spicy tacos, or creating some potted fish. ‘Cold fish’ may not be the sexiest phrase in the book, but this stuff is leftovers gold – and you’ll have no trouble transforming it into dishes that’ll get a very warm reception indeed.

One of the things I love about this easy recipe is its adaptability. All manner of cooked fish can be used, including white fish such as pollack, coley or sustainably caught haddock (even the remnants of a fish supper from the chippie), mackerel and sardines (freshly cooked or tinned and drained).

I used to think that you should never have more potato than fish in a fishcake, but in these more freewheeling days, I’m not so worried about that. As long as I have fish equivalent to at least half the weight of the spud, then I’m good to go.

250–400g mash or baked potato flesh (ideally mash should not be too smooth or creamy)

Put the mashed potato into a bowl and stir in the chopped parsley or chives and capers. Season well with salt and pepper and stir again.

Using a spatula, gently fold in the flaked fish and moisten with the egg. You may not need all of it – you don’t want the mixture to be too wet. (Any unused beaten egg can go to the dipping egg for the coating.)

Divide the mixture into four and gently shape, with floured or wet hands, into flat round cakes, 3–4cm thick.

Place the fishcakes on a plate and refrigerate for 30 minutes; this helps firm them up before crumbing. If you’re skipping that, just dust them lightly in seasoned flour and they’re ready to fry, or they can be chilled for a few hours before using.

If you’re crumbing the cakes, put the flour into a bowl and season well with salt and pepper. Put the beaten egg in a second bowl and the breadcrumbs in a third. Carefully dip each fishcake in flour, then in the egg and finally in the breadcrumbs. Press the eggy cake gently into the crumb, turn over, and repeat. Transfer carefully to a plate or board.

Pour about a 2mm layer of oil into a large non-stick frying pan. Add the butter and place over a medium-high heat. When hot, gently place the fishcakes in the pan and cook for 4–5 minutes on each side until golden brown and piping hot in the middle.

Spice them up A little curry paste or powder is a good alternative seasoning, especially if you’re using smoked fish leftovers.

Add anchovy If you have a couple of anchovy fillets lurking in the fridge, chop them finely and stir into the fishcake mix to add piquancy.

Change the coating For a finer coating, swap the breadcrumbs for fine cornmeal, panko breadcrumbs or matzo meal, omitting the flour and egg. Simply season the coating well with salt and pepper and use it to coat the fishcakes evenly all over.

These are a great way to use up the backbones of fresh mackerel or sardines left over after filleting; they look pretty dramatic too! You can also use cooked skeletons retrieved from baked or barbecued whole mackerel or sardines (but not the hard skeletons from big fish like bass and pollack).

Though they’re delicious and perfectly safe to eat, they are not something I would share with very small children.

Mix together all the ingredients for the seasoned flour in a bowl and tip onto a plate.

Bring a pan of water to the boil. Add the fish skeletons and blanch for 7–10 minutes to soften them slightly and strip them of any flesh still clinging to the bones. Drain in a colander then toss them in the seasoned flour to coat.

In a deep saucepan, wide enough to fit the length of the skeletons comfortably, heat a 4–5cm depth of oil to 180°C, or until a cube of dry white bread dropped into the oil turns golden in just under a minute.

Add the floured skeletons and fry until crisp and golden – this should only take a couple of minutes. Carefully remove them from the oil with tongs and lay on kitchen paper to drain.

Eat immediately, with a sprinkling of salt and a squeeze of lemon. They are also good with a hot and sweet chilli dipping sauce.

This is a by-product of my enthusiasm for making sushi and sashimi from fresh catches of bream, pollack, trout and bass. The skin and flesh trimmings of these (or any) fish are simply too good to waste. Crisply fried and well seasoned, they become delectable morsels – the bacon of the fish world. Any fresh fish skin will work – you could even ask your fishmonger to save some for you (it can be frozen). The fish needs to be descaled, which is most easily done when it is still whole. Any flesh left on the inside of the skin is a good thing – don’t scrape it off.

This mouth-watering sarny, topped with tartare sauce, gives crispy fish skin star billing.

At least 4 strips of fish skin, each about the size of a postcard, plus any boneless, fleshy fish trimmings

First make the tartare sauce. Mix together all the ingredients and season with salt and pepper to taste. Set aside.

To cook the fish skin and trimmings, heat the oil in a non-stick frying pan over a medium-high heat. Season the fish bits generously with salt and pepper. Put them in the pan and press the skins down with a spatula straight away, so they don’t curl up too much.

Fry, turning occasionally, until the skin and the bits of fish are golden and crisp: cook more than you normally would a piece of fish, to maximise the crispiness, but don’t let them burn. Drain on kitchen paper and season with a bit more salt and pepper if necessary.

Lightly butter the rolls or bread slices. Pile up the crispy fish bits on the bases and spoon on a generous dollop of tartare sauce. Press the top on your sandwich and eat straight away.

BLT version Use plain mayo and add a few crisp lettuce leaves and some tomato slices.

Fish skin ‘scratchings’ Either season the fish skin and fry it as above or put it into a roasting tin and roast for 20–30 minutes at 180°C/Fan 160°C/Gas 4, until crisp, turning after about 15 minutes. Serve with a dollop of tartare sauce or mayo. A great snack with a cold beer or cider.

This is a quick way to preserve bits and pieces of leftover cooked smoked fish for another dinner, another day. Try it with whatever smoked fish you have: mackerel, kippers, haddock, pollack or trout are all good. You can also use cooked leftovers of unsmoked but full-flavoured oily fish, like mackerel, sardines and trout. The recipe is easily scale-up-able, depending on how much fish you have, but you only need to increase the butter a little.

Carefully pick over the fish for any small bones, then put the flakes into a bowl with the herbs, lemon juice and cayenne.

Trickle over about three-quarters of the clarified butter and fold everything together gently with a rubber spatula – don’t mush it up too much. Taste and season with salt and pepper.

Spoon the mixture into a spotlessly clean bowl, large ramekin(s) or Le Parfait-type jar and press it down lightly with a fork.

Pour over the remaining clarified butter or ghee, giving the container(s) a sharp tap on the work surface to help eliminate any air pockets. Cover or seal and refrigerate.

The potted fish will keep for a couple of days in a bowl or ramekin, up to a week in a sealed jar. Bring it to room temperature about 30 minutes before serving, with warm brown toast and wedges of lemon.

Spike with horseradish Add about 1 teaspoon creamed horseradish sauce to the mixture if you want to give it a bit of bite.

Speedy version For a near-instant un-potted take on this, for immediate consumption, simply mix the fish flakes up with a dollop of crème fraîche, some chopped herbs if you have them, and perhaps some chopped capers and/or cornichons.

Clarified butter/ghee

Great for extending the potential of butter that’s slightly on the turn, these are also good solutions if you find you have more unsalted butter than you are likely to use. Sealed in a jar in the fridge, they can last for weeks, possibly months if you take care of them.

Clarified butter and ghee both have a higher smoke point than whole butter as the milk solids are removed, making them ideal for frying. They can also add buttery flavour to pasta, rice or other dishes, or be used as here to seal potted fish (or meat). About 1 kg butter will yield 800g ghee or clarified butter.

To cook up a batch, warm the butter gently in a saucepan. The solids will drop to the bottom and foam will rise to the top. At this point, if you’re making clarified butter, take it off the heat and let it sit for a minute. Skim off any foam and pour through a strainer lined with muslin into a clean jar. Seal and store in the fridge until needed.

To make ghee, simply proceed as above but let the butter cook for longer, until the clear butter is golden. Be careful not to let the solids at the bottom of the pan brown. Jar up as for clarified butter.

This is a terrific way to give a little leftover fish a rather smart second outing, as a platter of delicious canapés.

For the sauerkraut cream, mix the ingredients together and season with a couple of grinds of black pepper. Set aside.

To make the blinis, put the flour, baking powder and salt into a bowl and whisk to combine. Make a well in the centre and slowly pour in the beer, egg and oil, whisking as you go. Keep whisking until you have a smooth batter. It should be quite thick, so it will hold its own shape and not spread out too much when you pour it into the pan – if it’s too thick, just add a splash of water or milk.

Place a non-stick frying pan over a medium heat and brush with oil. When hot, drop in small ladlefuls of the batter, making each blini about 5cm across. Cook for 1–1½ minutes, until each one starts to rise and bubbles are showing on the surface. Flip over and cook for another 1–2 minutes until golden brown on both sides and cooked through. Remove to a warmed plate.

Repeat with the remaining batter, brushing the pan with a little more oil as you go. Keep the cooked ones warm as you complete the rest.

Put a spoonful of the sauerkraut cream on each blini, top with the flaked fish and add a grinding of black pepper. Finish with sprigs of dill or chopped parsley. Serve at once.

Using beer in the batter gives the blinis character, but you can use milk if you prefer.

This classic street food of Mexico’s Baja peninsula is usually made with fried fish, but it’s also a very tasty way to use up leftover cooked fish, whether it’s fried, barbecued, poached or grilled. I’ve even made extremely tasty tacos with the remains of take-away fish and chips.

1 jalapeño or other medium-hot green chilli, halved, membrane and seeds removed (for a milder salsa if preferred), finely chopped

Put the fish flakes into a bowl, sprinkle with the cumin and cayenne, squeeze on a little lime juice and season with salt and pepper. Turn over gently with a rubber spatula.

Thinly slice the other onion half and soak in a bowl of iced water for about 10 minutes to mellow the flavour. Drain, pat dry on kitchen paper and set aside for serving.

Mix the diced onion with the tomatoes, garlic, chilli, coriander, sugar and just enough oil to moisten the salsa. Taste and season with salt and pepper.

Warm the tortillas according to the package instructions. Pile the fish on top of the tortillas, along with dollops of the salsa, the avocado, red onion slices and coriander.

Roll up your tortillas and serve at once, with lime wedges, and hot sauce on the side for heat freaks.

Add shellfish Toss some cooked mussels or bits of squid in with the fish if you have them.

Add crunch If you have some white cabbage knocking about, finely shred a few leaves and scatter over the tacos with the onion.

Tostadas (as shown) Heat the tortillas for longer, until slightly crispy at the edges, then pile everything on top and tuck in, rather than roll up.

Rich, oily mackerel pairs particularly well with earthy lentils and the sharp bite of red onion in this simple, tasty salad.

Sprig of dill or tarragon, chopped, or a few basil leaves, roughly shredded (optional)

In a bowl, gently combine the mackerel, onion, lentils and herbs, trying not to break up the fish too much – it’s nicer if you keep it in flakes. Taste and season well with salt and pepper.

For the dressing, shake the oil, cider vinegar or lemon juice and mustard together in a screw-topped jar to combine and season to taste with salt and pepper. Trickle the dressing over the salad and toss gently.

Scatter some more chopped parsley over the salad and serve with lemon wedges on the side, if you like.

Open sandwich If you don’t have enough leftover mackerel for a full salad, use the assembly as a topping, especially on rye bread. Chop the onion quite finely and toss together with the fish, lentils and herbs, adding just enough mayonnaise to bind everything together. Season well with salt and pepper and serve with lemon wedges.

This is essentially a good fish stock, made with the heads (and bones if you like), bulked up with some lovely veg, and finished with the best fleshy pickings of the fish. You can often get fish heads free from the harbourside or your fishmonger if you are a regular customer. You want the fish trimmings you use to be spanking fresh, but apart from that, this is simplicity itself and endlessly customisable.

I’ve made great versions of this with the heads of pollack, coley, haddock, gurnard, bass, grey mullet and even large trout. Very oily fish like mackerel and sardines are best avoided.

2 fennel bulbs, core and tough outer leaves removed, finely sliced (any fronds saved)

3–4 good size fish heads (see above), plus fish skeletons and trimmings if available

1 or 2 bay leaves, 2 or 3 thyme sprigs and a few parsley stalks, tied together with kitchen string

Heat the oil or butter in a large heavy-based saucepan over a medium-low heat. Add the onion, celery and carrot with a pinch of salt and sauté very gently until softened, about 10 minutes. Add the fennel and potatoes and continue to cook gently, stirring, until they’re slightly softened, about 5 minutes. Meanwhile, rinse all the fish trimmings.

Add the fish trimmings to the pan, along with the herb bundle. Add just enough cold water to cover – no more than 1.5 litres. Bring to a very gentle simmer and skim off any scum that rises to the surface. Let the soup simmer very gently for about 15 minutes, until the veg are tender. Don’t let it boil hard as this can taint its flavour.

Remove from the heat. Scoop out and discard the bundle of herbs, then scoop out the fish heads and any skeletons or skin onto a board. Discard the skin and leave the heads and bones to cool a little.

Pick off the fish, discarding the bones and any shreds of skin as you go. You’ll find some surprisingly generous little caches of fish flesh around the cheeks, lips and ‘shoulders’ (where the head was cut off) and a few morsels on the skeletons too. Set the fish bits aside.

Reheat the pan of vegetable-y fish soup, if necessary, and stir in the lemon juice and chopped parsley. Taste and season with salt and pepper.

Distribute the salvaged fish morsels between warmed bowls and ladle over the veg and soup. Finish with some crème fraîche if you like, and scatter the chopped fennel fronds or parsley over the soup.

If you don’t have enough fish heads and skeletons to make the stock straight away, collect them in the freezer until you have assembled enough.

Veg options As well as, or instead of, the fennel, try adding finely chopped skinned, deseeded tomatoes, a handful of peas or sweetcorn, or some finely shredded, not-quite-good-enough-to-eat-raw lettuce. All of these are best added at the end of cooking.

Surely one of the most gratifying of all comfort foods, the gratin is the quintessential ‘bit of this, bit of that’ dish that lends itself beautifully to leftovers. Just add a seasonal green salad and you’ll have a delicious dinner.

About 500g cooked potatoes, mashed, or in crumbled pieces (if roasted or boiled)

200–300g smoked fish, such as mackerel, kippers, haddock or pollack, broken into large flakes

Preheat the oven to 200°C/Fan 180°C/Gas 6. Lightly oil an ovenproof dish, about 28cm in diameter.

Heat the oil in a medium-large, heavy-based saucepan over a medium-low heat. Add the onion, thyme, if using, and a good pinch of salt and sauté gently, until the onion is softened, about 15 minutes.

Pour in the wine (or half a glass of water) and bring to a simmer. Add the spinach or chard leaves, put the lid on and cook for a minute or two, until the greens are just wilted.

Remove from the heat and add the potatoes and cream or crème fraîche. Stir to combine and season with nutmeg, salt and pepper. Gently fold through the fish, then taste and adjust the seasoning.

Tip the fish mixture into the oven dish. Toss the breadcrumbs and cheese together and sprinkle over the top. Bake for 25 minutes until golden and bubbling.

Leave to stand for several minutes to cool slightly before serving, with a crisp green salad.

Veg options You can add other veg, as well as or instead of the spinach, such as halved cherry tomatoes, chopped spring onions, leftover roast roots and cooked peas.

Jansson’s temptation version Sauté the onions in the oil from a small tin of anchovies until softened, then add sliced cooked potatoes (not mash) and stir in the chopped anchovies from the tin, plus your flaked smoked fish leftovers. Season with pepper. Tip into the prepared gratin dish, trickle over a few tablespoonfuls of cream or crème fraîche and bake as for the gratin, for about 20–25 minutes until crisp and golden on top. Irresistible.