Hasselback Potato Gratin
WORKING TIME 45 minutes TOTAL TIME 2 hours, 15 minutes MAKES 6 to 8 servings 2 tablespoons olive oil, plus
more for baking dish
3 medium onions, thinly sliced Kosher salt and freshly ground black pepper 2 1/2 cups heavy cream 4 garlic cloves, thinly sliced 1 tablespoon chopped fresh thyme 1 tablespoon chopped fresh rosemary 8 ounces Gruyère, grated
(about 2 cups), divided 4 ounces Parmesan, grated (about 1 cup), divided 3 1/2 pounds Yukon gold potatoes, peeled and sliced 1/4-inch thick 1. Heat oil in a large skillet over medium heat. Add onions and season with salt and pepper. Cook, stirring occasionally, until golden brown, 30 to 40 minutes.
2. Preheat oven to 350°F.
Lightly grease a 3-quart baking dish. Combine onions, cream, garlic, thyme, rosemary, 1 2/3 cups Gruyère, and 2/3 cup Parmesan in a bowl. Season with salt and pepper.
3. Arrange potato slices vertically in prepared baking dish. Pour cream mixture over potatoes, making sure some of the mixture goes between the potatoes.
Cover with aluminum foil.
4. Bake until potatoes start to soften, 50 to 60 minutes. Remove foil and bake until potatoes are golden brown, 25 to 30 minutes. Sprinkle with remaining 1/3 cup Gruyère and 1/3 cup Parmesan. Bake until cheese is golden brown and bubbling, 5 to 10 minutes.