''Au gratin'' is a term most Americans associate with cheese. It is something of a misnomer for although cheese is often used, many au gratin dishes have no cheese at all.
Gratinm, or gratinem, means ''crusted'' in French, and a gratin can be any dish that is put into the oven or broiler to form a crisp golden crust.
The food is usually spread out in a shallow dish and topped with breadcrumbs, cheese, eggs, or a white sauce, which help make a browning surface.
Gratins usually cook quickly. They are good vehicles for leftovers. They are often made of shellfish, fish, meats, vegetables, or eggs, browned by a white or brown sauce.
A current way of serving fruit compote in some restaurants is to place raspberries or other fruit in a shallow dish, cover with a light egg or custard sauce, and put it under the broiler to brown the sauce and warm slightly, but not cook, the fruit.