Ingredients:3 tablespoons unsalted butter, melted
3 tablespoons extra-virgin olive oil
4 pounds russet potatoes, peeled
4 shallots, thickly sliced lengthwise
1/2 to 1 teaspoon red-pepper flakes (optional)
8 sprigs thyme
1. Preheat oven to 375 degrees. In a small bowl, combine butter and oil. Brush bottom of a round 9-inch baking dish with some butter mixture. With a sharp knife or mandoline, slice potatoes very thinly crosswise.
2. Arrange potato slices vertically in dish. Wedge shallots throughout. Sprinkle with salt and red-pepper flakes (if using); brush with remaining butter mixture. Bake 1 1/4 hours. Add thyme and bake until potatoes are cooked through with a crisp top, about 35 minutes more.