Put the fish with the bay leaf, onion slice, wine and just enough water to cover the fish, into a baking dish. Cover and cook in a preheated oven, l60°C/325°F/Gas Mark3, for 10 minutes.

Put the egg yolks, lemon juice, cayenne and paprika into a liquidizer, or food processor. Turn the machine on and gradually pour in the melted butter. Continue processing, until the hollandaise sauce is thick. Set aside.

Put the 15 g (1/2 oz) unmelted butter into a saucepan, melt over a gentle heat and stir in the flour. Cook gently for 1 minute.

Remove the fish from the baking dish and strain the cooking liquor onto the flour and butter in the saucepan, stirring well, to prevent lumps from forming. Cook this sauce gently until it is smooth and has thickened. Stir in the cream, but do not allow to boil. Season to taste.

Stir the crab meat into the fish stock sauce and pour this mixture into an flameproof dish. Lay the halibut fillets on top and cover these with the hollandaise sauce.

Brown the sauce under a hot grill before serving.