What Exactly Is a Gratin?

Yesterday, an urgent-sounding email from a friend pinged into my inbox: “A favor,” read the subject line, followed by, “I don’t understand gratin.” And then I realized that, darn it, I didn’t either.

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Our trusty copy of the Food Lover’s Companion told me that a gratin—sometimes written as gratinée or au gratin—is a very flexible dish; no wonder we weren’t quite sure how to classify it. But, the book said, they’re always baked in a shallow dish (sometimes called a “gratin dish”) and always topped with something that will crisp up when the dish goes into a hot oven or under a broiler, like cheese or buttery breadcrumbs. So here’s what we know:

1. A gratin is always baked and/or broiled in a shallow dish.
2. The topping is traditionally cheese or breadcrumbs, and they should get crispy under the broiler.
3. “Gratin” is derived from the French verb gratiner—to broil. Gratter (to scratch or scrape) is a close verb, and definitely suggestive of a gratin’s crispy crust. And in colloquial French, there’s the fun expression le gratin de la société—a.k.a., “the upper crust.”
4. Gratins sometimes come in disguise. 

The best known gratin dish is potatoes gratin (sometimes called pommes dauphinoises), and for good reason: Bake layers of sliced potatoes in a dish, top with grated cheese, buttered breadcrumbs, or both, and slide it under the broiler for a final scorch. You get the creamy potatoes, gooey cheese, and the crunchy breadcrumbs. It’s as good as it gets.

But what else can you make into a gratin? It turns out we make a lot of gratins without realizing they’re gratins.

There’s Julia Child’s very Genius rice-and-zucchini gratin, which, in Mastering the Art of French Cooking, Volume II, hides under the name “Tian de Courgettes au Riz.” It has at least as much zucchini as rice in it and is topped with a crispy, crispy layer of Parmesan cheese. And many tians are gratins! The Food Lover’s Companion says as much: Tians usually composed of thinly sliced and layered vegetables, baked in a shallow dish, and topped with cheese and/or breadcrumbs (just like a gratin!).

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Even macaroni and cheese is also a sort of gratin when topped with breadcrumbs (the best part!). Go ahead and call it pâte au fromage gratiné. If you want.

What else can you make au gratin? Just about everything (we’re lookin’ at you, leftovers), and they can go heavy and hearty (i.e. cream-filled and cheesy) or lighter, with just toasty breadcrumbs on top.

While hard vegetables like potatoes, cauliflower, and squash are the most common and the most traditional, there are chicken gratins and seafood gratins, pasta and rice gratins, and gratins made with softer vegetables like tomatoes, eggplant, or zucchini—or leafy greens, like kale, chard, and spinach. Sweet gratins don’t seem to have caught on yet—at least not in the same format as their savory cousins (though oat-topped crisps are pretty close). But if you try one—think sliced apples or pears (or sweet potatoes!) with a cinnamon sugar-breadcrumb topping—let us know. It’d be awfully good with a scoop of vanilla ice cream…

Photo of potato gratin by James Ransom; photo of tian by Karen Mordechai; photos of cauliflower and Brussels sprouts gratins by Bobbi Lin