This sauce is the perfect accompaniment for my poached eggs on potatoes with smoked haddock.
60g (2oz) carrot, finely diced
50g (1¾oz) celery, finely diced
60g (2oz) green beans, finely diced
50g (1¾oz) onion, finely diced
50g (3½ tbsp) butter
50ml (3½ tbsp) double (heavy) cream
1 egg yolk
juice of 1 lemon
salt and freshly ground pepper
30g (2 tbsp) butter
30g (3½ tbsp) plain (all-purpose) flour
500ml (2 cups) milk
First make a béchamel. Melt the butter in a small, heavy-based saucepan over a low heat, then add the flour, stir with a whisk, and cook gently for 2 – 3 minutes to make a white roux. Pour the cold milk on to the roux, as you whisk, and bring to the boil over a medium heat, whisking continuously. When the sauce comes to the boil, lower the heat and simmer gently for about 7 minutes, stirring at regular intervals.
Meanwhile, blanch the vegetables in boiling water for 1 minute. Refresh in cold water, drain and pat dry. Melt the butter in a small saucepan, add the blanched vegetables and sweat gently for 2 – 3 minutes.
Add the vegetables to the béchamel and let the sauce bubble for 2 – 3 minutes. Mix the cream and egg yolk together, then stir into the sauce. As soon it comes back to the boil, stir in the lemon juice and remove from the heat. Season the sauce with salt and pepper to taste. It is now ready to serve.
For an egg gratin, arrange sliced hard-boiled eggs in a well-buttered ovenproof dish, coat thickly with sauce écossaise and heat in the oven at 180°C/350ºF/Gas 4 for 5 minutes.