Whether you know it as potatoes au gratin or scalloped potatoes, this bubbling casserole of creamy sliced potatoes and cheese will warm up any cold night. Start the cooking process on the stove by getting the sauce and potatoes warmed through. Then layer the potatoes, sauce, and cheese in the dish and bake until golden brown. Serve alongside glazed ham or steak for a rich and comforting meal.
Special equipment: If you have a mandoline, this is the ideal moment to pull it out so you get uniformly thin potato slices.
Game plan: This recipe can be completely made ahead. Cool to room temperature, cover with plastic wrap or aluminum foil, and refrigerate for up to 2 days. Rewarm uncovered in a 350°F oven for about 30 to 40 minutes.
4 cups (1 quart) half-and-half
2 medium garlic cloves, minced
1 tablespoon plus 2 teaspoons kosher salt
1/2 teaspoon freshly ground black pepper
1/2 teaspoon finely chopped fresh thyme leaves
4 pounds russet potatoes
2 cups shredded Gruyère cheese (about 5 ounces)
2 tablespoons unsalted butter (1/4 stick), cut into 8 pieces, plus more for coating the baking dish
Heat the oven to 350°F and arrange a rack in the upper third. Coat a 13-by-9-inch baking dish with butter; set aside.
Place the half-and-half, garlic, salt, pepper, and thyme in a large, wide pot or Dutch oven. Peel and cut the potatoes into 1/8-inch-thick slices and add them to the pot. Bring the mixture to a simmer over medium heat, gently folding the potatoes into the sauce occasionally (this helps the potatoes heat evenly), about 20 minutes total.
Using a slotted spoon, transfer half of the potatoes to the prepared baking dish and arrange them in an even layer. Evenly sprinkle with half of the cheese. Transfer the remaining potatoes to the dish, arranging them in an even layer. Pour the half-and-half mixture from the pot over the potatoes. Sprinkle with the remaining half of the cheese and scatter the butter pieces on top.
Bake uncovered until the potatoes are very tender and the top of the casserole is dark golden brown and bubbling, about 1 hour (cover the dish with foil if the top starts to get too brown). Remove to a wire rack and let sit for 10 minutes before serving.