An especially nice fish dish for the uninitiated. The sauce is an impressively rich but easy one.
Arrange fillets of cod in a small buttered baking dish. Sprinkle with mushrooms, parsley, shallot, salt, and pepper. Moisten with white wine. Bake at 350 degrees F for 15 minutes or until fish flakes when tested with a fork; remove fish to serving platter. Combine flour and milk with the remaining juices in the baking pan. Cook, stirring, until the sauce is smooth and slightly thickened. Pour sauce over fish and garnish with lemon slices, cucumber balls, and tomato wedges.