Cooking a stock for longer than suggested in the recipe does not make it better – quite the reverse. With lengthy cooking, a stock becomes heavy and loses its flavour; this applies particularly to fish stocks, which can also acquire a bitter taint.
MAKES 2 LITRES
1.5kg white fish bones and trimmings (from sole, turbot, brill, whiting, etc.), cut into pieces
50g butter
2 leeks (white part only), well washed and thinly sliced
75g onions, thinly sliced
75g button mushrooms, thinly sliced
200ml dry white wine
2.5 litres cold water
1 bouquet garni
2 lemon slices
8 white peppercorns, crushed and tied in muslin
Rinse the fish bones and trimmings under cold running water, then drain.
Melt the butter in a large saucepan, add the sliced vegetables and sweat gently over a low heat for a few minutes.
Add the fish bones and trimmings and allow to bubble gently for a few moments, then pour in the white wine. Cook until it has reduced by two-thirds, then add the cold water. Bring to the boil, then lower the heat, skim the surface and add the bouquet garni and lemon slices.
Simmer very gently for 25 minutes, skimming as necessary. About 10 minutes before the end of cooking, add the muslin-wrapped peppercorns.
Gently ladle the stock through a fine chinois into a bowl and cool over ice. Refrigerate and use within 2 or 3 days, or freeze for up to 3 months.