In the culinary arts, the term au gratin (pronounced "oh-GRAH-tan") refers to a dish that is baked with a topping of seasoned breadcrumbs and cheese. The au gratin topping should be golden brown, which can be achieved by baking or by placing the dish under a broiler.
Potato gratin is a popular recipe that is prepared in the au gratin style. Vegetables such as cauliflower, green beans, eggplant or tomatoes can be prepared au gratin. Fish and seafood is also sometimes prepared au gratin.
For some vegetable gratin recipes, you'd cook the vegetables partially and then bake them in the gratin topping. For instance, for a cauliflower gratin, I'd first toss the cauliflower florets in olive oil and Kosher salt, then roast them on a flat sheet pan at 425° for about 15 to 20 minutes.
Then I'd transfer them to a shallow baking dish, cover with a Gruyère cheese sauce (a simple Béchamel sauce with grated Gruyère added), and top with seasoned bread crumbs and Parmesan cheese along with dots of butter. Then bake at 375° until the top is golden brown.
Also Known As: Gratinée