Brussels Sprouts and Potato Gratin

A traditional, French gratin hasn’t any cheese; the potato starch naturally thickens the cream, creating a luscious, creamy side dish.

6 tablespoons unsalted butter, plus additional for greasing the pan

1 large red onion, chopped

1 pound Brussels sprouts, stems and outer leaves removed, then thinly sliced, almost shredded

21⁄2 pounds yellow-fl eshed potatoes, preferably Yukon golds

1 tablespoon stemmed thyme or 2 teaspoons dried thyme

1 teaspoon salt

1⁄2 teaspoon freshly ground black pepper

1⁄4 teaspoon grated nutmeg

2 cups heavy cream

1 cup vegetable broth

• Position the rack in the center of the oven and preheat the oven to 350°F. Lightly butter a 13x9-inch baking dish; set aside.
• Melt 3 tablespoons butter in a large skillet over medium heat. Add the onion, reduce the heat to low, and cook, stirring often, until golden, about 10 minutes.
• Add the Brussels sprouts and raise the heat to medium. Cook, stirring often, until softened, about 6 minutes. Set aside off the heat.
• Peel the potatoes, then thinly slice them the long way into strips no more than 1⁄4 inch thick. It’s best to use a mandoline, but you can use a knife if it’s quite sharp.
• Layer half the potatoes across the bottom of the buttered baking dish. Spread the Brussels sprouts mixture evenly over the potatoes. Sprinkle evenly with the thyme, 1⁄2 teaspoon salt, the pepper, and nutmeg; then top with the remaining potato slices. Sprinkle the remaining 1⁄2 teaspoon salt over the dish, then pour the cream and broth evenly over the dish. Dot with the remaining 3 tablespoons butter.
• Bake until the potatoes are golden and tender and most of the liquid has been absorbed, about 11⁄2 hours. During the last 30 minutes, use a large spoon to catch some of the juices and cream bubbling up between the potatoes; baste the potatoes two or three times to moisten them on top.

Makes 8 servings