Preparation Preheat oven to 350°F with rack in upper third. Butter a 3-to 4-quart shallow baking dish. Peel potatoes and thinly slice (about 1/16 inch thick) with slicer. Toss with butter, oil, 1 teaspoon salt, and 1/2 teaspoon pepper in a large bowl. Transfer to dish and cover tightly with foil. Bake 20 minutes. Remove foil and increase oven temperature to 450°F, then continue to bake until top is browned and crisp, about 25 minutes more. Cooks’ note:Potatoes can be baked 2 hours ahead and kept at room temperature. Reheat, loosely covered with foil, in a 250°F oven.
Preparation Preheat oven to 350°F with rack in upper third. Butter a 3-to 4-quart shallow baking dish. Peel potatoes and thinly slice (about 1/16 inch thick) with slicer. Toss with butter, oil, 1 teaspoon salt, and 1/2 teaspoon pepper in a large bowl. Transfer to dish and cover tightly with foil. Bake 20 minutes. Remove foil and increase oven temperature to 450°F, then continue to bake until top is browned and crisp, about 25 minutes more. Cooks’ note:Potatoes can be baked 2 hours ahead and kept at room temperature. Reheat, loosely covered with foil, in a 250°F oven.