Preparation Peel the potatoes and, using a food processor fitted with the slicing blade or a mandoline, slice them very thin, transferring them as they are sliced to a large bowl of cold water. Drain the slices and pat them dry between paper towels. Generously brush the bottom and side of a 9-inch heavy ovenproof skillet, preferably non-stick, with some of the butter and in the skillet arrange the slices, overlapping them slightly, in layers, brushing each layer with some of the remaining butter and seasoning it with salt and pepper. Cover the layered potato slices with a buttered round foil, tamp down the assembled potato cake firmly, and bake it in the middle of a preheated 425°F. oven for 30 minutes. Remove the foil and bake the potato cake for 25 to 30 minutes more, or until the slices are tender and golden. Invert the potato cake onto a cutting board and cut it into 8 wedges.