gratiner

Gratiner comes from French gratin, which comes from gratter (to scrape), from Frankish *krattōn. A gratin is the golden crust that forms on the surface of a dish baked or broiled at high temperature. The word names the crust, not the dish — what you eat is the gratin; what you cook is the gratiné. The act of scraping is the act of eating: the best part is the crust that sticks to the dish and must be scraped off.

The technique is simple: top a prepared dish with breadcrumbs, cheese, butter, or a combination, and expose it to high heat (under a broiler or salamander) until the surface browns and crisps. The Maillard reaction and caramelization produce the golden color. The fat promotes browning. The result is a contrasting texture: crisp crust over soft interior. Gratin dauphinois — sliced potatoes baked with cream and a browned cheese top — is the canonical gratin, though the technique applies to any dish.

Auguste Escoffier classified gratins in his Guide Culinaire (1903), distinguishing between gratins complets (complete gratins, browned in the oven from start to finish) and gratins légers (light gratins, where a separately cooked dish receives a topping browned under the salamander). The classification reflects the French professional kitchen's need to name every variation of every technique. The word gratin already implied browning. Escoffier made the browning systematic.

The word au gratin entered English as a menu descriptor: 'potatoes au gratin' means potatoes with a browned crust. The phrase has been so widely adopted that many English speakers do not know it is French. The spelling 'au grotten' has appeared on restaurant menus. The crust survives the misspelling.