Preheat the grill (broiler) to high.

Arrange the fish steaks in the lined grill (broiler) pan. Cut half the butter into small pieces and dot over and around the fish. Place the pan under the grill (broiler) and grill (broil) for 3 to 5 minutes on each side. Using tongs, transfer the fish steaks to a large, warmed serving dish. Keep hot while you prepare the sauce.

Melt the remaining butter in a small saucepan. Remove from the heat and stir in the flour to form a smooth paste. Gradually stir in the stock, orange juice and seasoning and return the pan to low heat. Bring to the boil, stirring constantly. Cook for 2 to 3 minutes, stirring constantly, or until the sauce is thick and smooth.

Pour the sauce over the fish and garnish with the orange slices. Serve at once.