If you're a cheese lover, make sure to scan your next menu for the phrase au gratin. 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. It's a versatile topper that's an easy way to add flavor and of course, more cheese, to numerous dishes.
Potato gratin is a popular recipe that is prepared in the au gratin style. The basic method is to slice potatoes thinly (about 1/8-inch thick) and layer them in a buttered dish with alternating layers of cream and cheese. Gruyère is a good choice for this dish or a combination of Gruyere and Parmesan. It helps to season each layer as you build it, and press down the layers before adding the next one. Finally, top with cheese and seasoned bread crumbs and bake.
Some recipes skip the breadcrumb topping, but to me, the breadcrumbs are key, for the flavor and texture they add. They can be helpful in the cooking process as well because the fat can separate from the cheese while it bakes. The breadcrumb topping helps to soak up some of the fat.
Vegetables such as cauliflower, green beans, eggplant or tomatoes can be prepared au gratin. Unlike with potatoes, some vegetable gratins involve cooking the vegetables partially and then baking them in a dish with the gratin topping. For instance, for a cauliflower gratin, I'd first toss the cauliflower florets with olive oil and Kosher salt, then roast them on a flat sheet pan at 425 F 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 dabs of butter. Then bake at 375 F until the top is golden brown.
Sole Au Gratin
Fish and seafood is also sometimes prepared au gratin. An example of this preparation is the classic sole au gratin. To make it, you'd line the bottom of your baking dish with what is called duxelles, or chopped mushrooms that have been sauteed in butter until you've cooked the moisture all the way out of them. Some cooks even go so far as to press the cooked mushrooms in a piece of cheesecloth to squeeze out any excess moisture.
Then the fillets of the sole are laid over the duxelles, seasoned with salt and pepper and then draped with a sauce, often a white wine mushroom sauce made from fish stock. Finally, seasoned breadcrumbs and dots of butter go on top, and it's baked until the fish is cooked and the topping is brown.
If you want to get even fancier, you could split a lobster tail lengthwise top it with seasoned breadcrumbs and broil it.