What is a gratin?
In French, the word gratin originally referred to the tasty crust left behind in a pan after baking, which was scraped off and eaten as a bonus for the chef. Now, cooking something au gratin can mean preparing a dish that is cooked from scratch in the oven, like a gratin dauphinois made with potatoes and cream; or combining several cooked ingredients in casserole form, like a baked pasta dish. A gratin is usually topped with grated sharp cheese and/or breadcrumbs. Adding just cream will also produce a lightly browned crust if baked in high heat. Technically, macaroni and cheese is a gratin, in that a protective crust forms while it bakes, giving it a lightly browned and crunchy topcoat, while keeping the rest of the dish moist. Gratins are served straight from the dish; hence the term gratin dish, which refers to an (often oval-shaped) oven-safe serving pan. That old-fashioned favorite, onion soup gratinée, is made by pouring soup into oven-safe tureens, topping them with toasted bread
