Ingredients
1 pound Yukon gold potatoes, thinly sliced
12 ounces sweet potatoes, thinly sliced
1 green apple (6 ounces), cored and grated
3 leeks, white and pale-green parts only, halved lengthwise, sliced 1/8 inch thick, and rinsed well
1 tablespoon extra-virgin olive oil
Coarse salt and freshly ground pepper
2 ounces grated Gruyere cheese (1 cup)
Preparation
Preheat oven to 350 degrees. Toss together potatoes, sweet potatoes, apple, leeks, oil, and 1 teaspoon salt. Season with pepper. Transfer to a 9-by-12-inch oval baking dish, spread into a thin layer, and cover with parchment-lined foil. Bake for 15 minutes. Raise oven temperature to 400. Remove, uncover, and top with Gruyere. Bake until bubbling and top is browned, about 30 minutes.
