Any white fish can be used, such as coley, cod or haddock. If you are feeling extravagant, use sole, turbot, hake or halibut. Parsley or watercress sauce can replace the tomato sauce if preferred.
Melt the butter in a small, heavy saucepan, add the flour and stir until smooth. Pour on the cream and fish stock and cook until smooth and free from lumps, stirring continuously. When the mixture is thick and leaves the sides of the pan, remove it from the heat. Cut the fish fillet into pieces, and put it in a food processor with the seasoning, lemon juice, egg yolks and thick sauce. Process until smooth. Rub the mixture through a fairly fine wire sieve into a bowl. (This is a somewhat tedious process but necessary for a smooth, velvety texture to the mousseline.) Beat the egg whites until stiff, and fold into the fish mixture. Lightly butter a small soufflé dish, timbale or other ovenproof dish and half-fill with the mixture. Cover with a circle of greaseproof paper, and cook in a bain-marie in a preheated oven at 180°C / 350°F / Mark 4, or on the hob for 18–20 minutes, until risen and firm to the touch. Remove from the heat, lift the dish out of the water, and allow the mousseline to stand and settle for a minute or two. Turn it out on to a heated plate and pour the tomato sauce around it before serving.
© 1995 Frances Bissell. All rights reserved.