Layers of melted cheese and caramelized onions make this sweet potato gratin extra indulgent.
Sweet Potato Gratin with Caramelized Onions
Makes 6 to 8 servings
Ingredients
- 2 teaspoons unsalted butter
- 1 clove garlic, halved
- 2 teaspoons vegetable oil
- 2 cups chopped yellow onion
- 2 teaspoons finely chopped fresh rosemary
- ¾ teaspoon kosher salt, divided
- 1 tablespoon water
- 2¾ pounds medium sweet potatoes, peeled and thinly sliced
- ¼ teaspoon ground black pepper
- ⅓ cup chicken broth
- ½ cup shredded fontina cheese
- ⅓ cup panko (Japanese bread crumbs)
- ¼ cup freshly grated Parmesan cheese
- Garnish: finely chopped fresh rosemary
Instructions
- Preheat oven to 350°. Rub the inside of a 2½-quart cast-iron baking dish with butter and garlic.
- In a 10-inch cast-iron skillet, heat oil over medium heat. Add onion; cook until lightly browned, about 3 minutes. Stir in rosemary and ¼ teaspoon salt. Cover; reduce heat to medium-low. Cook until onions are deep brown and tender, about 20 minutes, adding 1 tablespoon water to prevent sticking to pan, if necessary. Remove from heat.
- In a large bowl, toss together potatoes, pepper, and remaining ½ teaspoon salt. Layer sweet potatoes and onions in prepared dish. Pour broth over sweet potatoes. Cover tightly with foil.
- Bake until sweet potatoes are tender, about 50 minutes. Uncover; sprinkle with fontina, bread crumbs, and Parmesan.
- Increase oven temperature to 400°. Bake until cheese is melted and bread crumbs are lightly browned, about 7 minutes more. Let stand for 10 minutes before serving. Garnish with rosemary, if desired.
