Cut the rock salmon into 2.5 cm (1 inch) chunks. Put these into an ovenproof dish with the lemon juice, bay leaf, onion, peppercorns and just enough water to cover. Cover with a lid and poach for about 10 minutes in a preheated oven, 180°C/350°F/Gas Mark 4.

Melt the butter in a saucepan and stir in the mushrooms, pepper, shallot, paprika and garlic. Cook gently, until the pepper begins to soften.

Stir the flour into the mushrooms and peppers. Gradually add the milk, stirring until the sauce has thickened.

Remove the fish from the dish and strain off the liquor. Stir enough of this liquor into the pepper sauce to make it of coating consistency Add the parsley, thyme and tomato puree to the sauce and simmer for 2 - 3 minutes. Season to taste.

Arrange the hot, cooked pasta on a serving plate and place the rock salmon on top. Coat with the paprika sauce, and spoon over the sour cream, or yoghurt, to serve.