Lightly butter and base line a 1.6 litre (2 3/4 pint) loaf tin or terrine.

Melt 40 g (l 1/2 oz) of the butter in a saucepan. Add the garlic. Stir in 45 ml (3 tbsp) of the flour and cook gently, stirring, for 2 minutes. Remove from the heat and gradually stir in 450 ml (3/4 pint) of the milk. Bring to the boil, stirring constantly, then simmer for

2 minutes until thick and smooth.

in a blender or food processor, puree the sauce, raw chopped fish, cream, anchovy essence, eggs and yolk. Season lightly.

Spoon half the fish mixture into the tin. Sprinkle with parsley and half the prawns. Spoon in the rest of the fish mixture. Cover tightly with buttered greaseproof paper.

Place in a roasting tin with hot water to come halfway up the sides of the terrine. Cook in the oven at 150°C (300°F) mark 2 for about l 3/4 hours.

Just before the terrine is cooked, make the sauce. Put the remaining 25 g (1 oz) butter, 30 ml (2 tbsp) flour and remaining milk in a saucepan. Heat, whisking continuously, until the sauce thickens, boils and is smooth. Simmer for 1 - 2 minutes. Stir in the grated cheese and remaining prawns. Season to taste.

invert the loaf on to a warm serving dish and tilt slightly to drain off juice. Remove cooking container. Spoon a little sauce over terrine and garnish with watercress and prawns. Serve the rest separately.