Combine butter, flour, milk, salt, and pepper. Cook over hot water until thick and smooth. Add meat. Remove from fire. Stir until blended. Add well-beaten egg yolks. Cool. Fold in stiffly beaten egg whites. Pour into well-oiled casserole. Place in pan of warm water. Bake in moderate oven (375 F) 20 minutes, or until an inserted knife comes out clean. Serve immediately. 6 servings.
