Preheat the oven to 400°. In a 9-inch heavy-bottomed ovenproof skillet, heat 2 tablespoons of the oil. Add the potatoes and smooth the top. Cook over high heat until a crust starts to form, about 3 minutes. Transfer the skillet to the oven and bake for about 20 minutes, or until the cake is browned and crusty on the bottom.