Au gratin is a French term that refers to a dish that is topped with a browned crust of breadcrumbs, cheese, or a combination of the two. The term “gratin” itself means “crust” in French, and it is used to describe any dish that has a crispy or browned top layer.

In cooking, the term “au gratin” typically refers to a dish that is made by layering thinly sliced vegetables or potatoes with a creamy sauce and grated cheese, then baking it in the oven until the cheese is melted and bubbly and the top is golden brown and crispy. The dish may also be seasoned with herbs, spices, or other flavorings, depending on the recipe.

Au gratin dishes are often served as a side dish or as a main course. Some popular variations of the dish include potato au gratin, cauliflower au gratin, and macaroni and cheese au gratin. The dish is popular in many countries, including France, the United States, and Canada, and it is often served during the holidays or other special occasions.