Leek and Sweet Potato Gratin
You can bake this a day ahead, then reheat it in a 350 degree oven for 20 minutes while the turkey rests. Store it in the refrigerator overnight, then bring it to room temperature for an hour before popping it in the oven.
Time: 1 hour, 30 minutes
Yield: 8 servings
- 2 tablespoons unsalted butter, more for greasing the pan
- 3 large leeks, trimmed and halved lengthwise
- 1 1/2 pounds peeled Yukon Gold potatoes
- 1 pound peeled sweet potatoes
- 1 teaspoon kosher salt, plus additional to taste
- 3/4 teaspoon ground black pepper, plus additional to taste
- 2 tablespoon sage, chopped
- 1 1/4 cup crème fraiche
- 1/2 cup milk
- 2 fat garlic clove, finely chopped
- 2 bay leaf
- 1/4 teaspoon freshly ground nutmeg
- 4 eggs, lightly beaten
- 1 1/4 cup Gruyère cheese, grated
1. Heat oven to 350°F. Wash the leeks to remove any grit and slice thinly crosswise.
2. Melt the 2 tablespoons butter in a large skillet over medium heat. Add leeks, 1/4 teaspoon salt and pepper, and sage. Cook, stirring, until leeks are tender and golden, 5 to 7 minutes, remove from skillet and reserve.
3. Meanwhile, using a mandoline or sharp knife, slice the potatoes and sweet potatoes into rounds, 1/8-inch thick. Toss with remaining 3/4 teaspoon salt and 1/4 teaspoon pepper.
4. Add cream, garlic and bay leaf to the skillet, scraping up browned bits of leeks from the bottom of the pan. Simmer gently for 5 minutes, then remove from heat and discard bay leaf.
5. In a large, heat-proof bowl, lightly beat together eggs and nutmeg. Slowly pour hot cream into eggs to combine, whisking while pouring, and reserve the mixture.
6. Wipe out skillet, grease with additional butter. In the skillet, carefully layer half the potatoes, seasoning each layer lightly with salt and pepper, then scatter leeks on top. Pour half of the egg and cream mixture over leeks. Top with remaining potatoes, continuing to season each layer with salt and pepper, top with leeks and Gruyère.
7. Cover with aluminum foil and transfer to the oven. Bake for 40 minutes, uncover and bake until the cheese is bubbling and golden, 20 to 25 minutes longer. Let cool slightly before serving.
