BAKED FLOUNDER À LA ST. MALO

Put the cleaned fish into a buttered baking-dish with chopped onions, parsley, salt, pepper, a tablespoonful of butter and two cupfuls of cider. Add also a little mussel or oyster liquor if at hand. Bake for half an hour in a moderate oven, basting as needed. Drain the sauce, thicken with a tablespoonful of butter cooked with an equal quantity of flour, add more butter and a squeeze of lemon-juice. Pour the sauce over the fish and serve.