Au gratin is a term that, in America, is usually associated with cheese. But the term may refer to any light but thorough topping of fine fresh or dry bread crumbs or even crushed cornflakes, cracker crumbs, or finely ground nuts on scalloped dishes or casseroles. These dishes, usually combinations of cooked shellfish, fish, meats, vegetables, or eggs, bound by a sauce and served in the dish in which they were cooked, are then browned in the oven or under the broiler to form a crisp golden crust. Set the casserole dish or baking dish on a piece of foil, shiny side down to deflect the heat, or just set it on a baking sheet.