Skin the haddock fillet, remove any bones and cut the fish into
Add the milk and the butter in small pieces, then cover with a buttered paper. Place in the centre of a moderately hot oven (200°C., 400°F., Gas Mark 6) and bake for 20 minutes or until the fish flakes.
Towards the end of the cooking time prepare the sauce. Melt half the butter in a saucepan over low heat. Stir in the flour and cook gently for a few moments. Gradually stir in the milk, beating well all the time to get a smooth sauce. Bring up to the boil, stirring all the time. Season with salt and pepper and allow to simmer gently for about 3–4 minutes.
When the fish is cooked, lift the pieces out on to a hot serving dish and strain the juices from the baking dish into the sauce.
Draw the pan of sauce off the heat and beat in the remaining butter.
The sauce should be smooth and shiny. Pour over the fish, sprinkle with chopped parsley and serve.