There’s something irresistible about a dish of vegetables suspended in a creamy, rich sauce, maybe a little melted cheese, all of it hidden and bubbling under a crisp golden-brown crust. This is the glorious gratin.
Gratin is a French word that means the crust that forms on top of a dish when you brown it in the oven or under the broiler. The term originally comes from the French word “gratter” (to scrape), which refers to the need to scrape the crunchy bits of cooked food off the bottom of a dish so as not to waste it.
The best-known gratin dish is potatoes gratin. Gratins sometimes come in disguise. It turns out we make a lot of gratins without realizing they are gratins. While hard vegetables like potatoes, cauliflower, and squash are the most common, 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 Swiss chard, kale, and spinach. Make a gratin with a single ingredient, or mix a few different items together for variety. How about potato-butternut squash, potato-parsnip, potato-rutabaga, potato-sweet potato, or potato-turnip?
The gratin can be refined or rustic, combining just a few ingredients or a sophisticated harmony of flavors. There are only three fundamental components to any gratin—the base ingredient, the liquid, and the top crust.
The best gratin potatoes are medium-starch, buttery Yukon Golds. As opposed to russets, which drink up all the liquid and make a drier gratin, and waxy potatoes, which don’t absorb enough, Yukon Golds soak up plenty of liquid but still leave discernible layers in your finished gratin. In addition, I suggest you pre-cook the potato slices in vegetable broth or water. The potato should retain some of the crunch in the center. By doing this, the potatoes will be fully cooked when removed from the oven.
For a classic rich, creamy, indulgent gratin, heavy cream is vital. But you can also use light cream or a mixture of cream and milk. An all-milk or milk-broth gratin will tend to curdle, but you can go with all-broth for the lightest option.
Changing It Up
A salty cured meat like pancetta or bacon isn’t essential, but it gives the gratin another layer of flavor. If you’ve chosen ham, Canadian bacon, or prosciutto for your meat, they need no pre-cooking. If you’ve selected bacon, pancetta, or sausage, heat a large skillet over medium-high heat, add 4 to 6 oz. meat and cook until browned and fully cooked. If using bacon or sausage, crumble it when it’s cool.
If using vegetable add-ins, they are sautéed until tender and then layered between the root vegetables. Consider adding in onion, shallots, leeks, fennel, mushrooms artichoke hearts, or garlic. Just make sure anything you choose complements your base ingredient.
Fresh green herbs or a sharp spice can help break up the richness of the gratin. Try the addition of chives, herbes de Provence, parsley, thyme, rosemary, smoked paprika, grated nutmeg, or a pinch of cayenne pepper. Some recipes recommend steeping the herbs in the hot cream mixture that is strained for a flavorful dish.
If you want to add cheese, keep in mind that Gruyère (pronounced “groo-YAIR”) is a classic addition. Gruyère is a smooth-melting type of Swiss cheese that’s made from whole cow’s milk and generally cured for six months or longer. Gruyère isn’t the most affordable cheese. If you need a substitute for Gruyère cheese, you could try Emmental, Jarlsberg, Beaufort, comté or raclette. Other cheeses will bring new dimensions and are worth trying, so use cheddar, fontina, Gouda, Havarti, or mild blue cheese. The cheese can be melted into the sauce or crumbled into the dish as the gratin is assembled for baking.
Finally, in order to qualify as a gratin, the casserole should have a golden brown top crust. Traditionally, this is a scattering of breadcrumbs and cheese, but sprinkling the gratin with an optional topping like chopped nuts is another alternative for both added texture and flavor.
Gratins are perfect for a make-ahead meal. Assemble the entire gratin in advance and store it in the refrigerator. Just pop it in the oven to bake when mealtime approaches. Whichever way you cook your crunchy-topped gratin, with cheese or without, it’s the perfect dish to ease into the colder weather – the side dish that goes with absolutely everything!