Scalloped Potatoes

Arrange a rack in the upper third of the oven and heat the oven to 375ºF. Coat a 9x13-inch baking dish with butter.

Peel 3 pounds russet potatoes, then cut crosswise with a chef’s knife or on a mandoline into thin (1/8-inch) thick slices. Place in a large pot or Dutch oven (preferably wide). Add 3 1/2 cups half-and-half, 2 1/2 teaspoons kosher salt, 2 finely choppped garlic cloves, and 1/2 teaspoon fresh thyme leaves. Bring to a simmer over medium heat, gently folding the potatoes into the sauce every few minutes to bring the potatoes at the bottom to the top, 12 to 13 minutes. Turn off the heat.

Transfer the potatoes and sauce into the baking dish and arrange into an even layer. Cut 2 tablespoons unsalted butter into 8 pieces and scatter evenly over the top.

Bake until the potatoes in the center are knife tender, 50 to 55 minutes. Turn on the broiler and broil until the top is browned in spots, 3 to 5 minutes. Let cool for 5 minutes for the sauce to thicken slightly before serving.

Using a slotted spoon, transfer about half of the potatoes into the baking dish and arrange into an even layer. Sprinkle with 3 ounces of the shredded Gruyère cheese. Repeat layering the remaining potatoes, then pour any remaining sauce evenly over the top. Sprinkle with the remaining 3 ounces shredded Gruyère.

Bake until the potatoes in the center are knife tender and the top is golden brown, 55 to 60 minutes. Let cool for 5 minutes for the sauce to thicken slightly before serving.

Substitutions: The half-and-half can be substituted with 1 3/4 cups whole milk plus 1 3/4 cups heavy cream.Make ahead: The scalloped potatoes can be completely made ahead up to 2 days ahead. Let cool to room temperature, cover with plastic wrap or aluminum foil, and refrigerate. Drizzle with a little milk or half-and-half, and reheat uncovered in a 350°F oven until warmed through, 30 to 40 minutes.Storage: Leftovers can be refrigerated in an airtight container for up to 4 days.