Salt and black pepper Preheat oven to 180ºC Oil bottom of an 8x10 inch baking dish. Using a vegetable slicer or very sharp knife, slice sweet potatoes as thin as possible. Slice baking and red skin potatoes as you need them, to prevent browning. Cover bottom of dish with a layer of Idaho potato slices, slightly overlapping. Drizzle with oil, sprinkle with garlic and cheeses and season with salt and pepper. Top with sweet potatoes, then red skin potatoes, seasoning and sprinkling each layer. Continue layers until all potatoes are used up, reserving enough cheese to fully cover top layer. Cover with foil and bake until potatoes are fork tender. Remove and let sit before cutting.