Ingredients
65g/2½oz butter
15g/½oz plain flour
4 x 225g/8oz turbot steaks, skinned
175g/6oz small button mushrooms, wiped clean and halved
12 salad onions or large spring onions, trimmed and cut into 4cm/1½in pieces
600ml/1pint fish stock
1 egg yolk
50ml/2fl oz double cream
1 tsp fresh lemon juice
1 tsp chopped parsley
salt and freshly ground white pepper

Method
1. Make a beurre manie by working the flour with 15g/½oz of the butter. Season the turbot with a little salt.
2. Melt the rest of the butter in a shallow oven-to-table pan, just large enough to hold the fish steaks side by side.
3. Gently cook the mushrooms and onions for about four minutes, seasoning them with salt. Using a slotted spoon, remove them to a plate and add the turbot to the pan. Turn up the heat a little and let the steaks brown slightly on either side. Add the fish stock, cover and poach the steaks for about 6 minutes.
4. Lift out the turbot and pour the cooking liquid into a small pan, then return the turbot and the vegetables to the main pan. Keep warm while you complete the sauce. Rapid boil the cooking liquid until it has been reduced by about half, then stir in the beurre manie and cook, stirring continuously, for about 3 minutes until the sauce has thickened. Take off the heat.
5. Mix the egg yolk and cream together in a small bowl, then stir into the sauce. Reheat gently, but don't let it come to the boil. Add the lemon juice and season to taste with the salt and white pepper. Pour the sauce over the fish and vegetables in the pan. Sprinkle with chopped parsley and serve with some steamed new potatoes and a soft green lettuce salad.