Pommes Anna - unsalted butter

Method

• Brush the bottom of a 9-inch heavy oven-proof non-stick or well-seasoned cast-iron skillet with 1 tablespoon of the butter.
• Peel 1 potato, slice it thin, using a food processor fitted with the slicing blade, or a mandoline or similar slicing device, and pat the slices dry quickly.
• Arrange the slices, overlapping them slightly, in layers in the skillet, brushing each layer with some of the remaining 3 tablespoons butter and seasoning it with salt and pepper.
• Peel, slice, pat dry, and arrange the remaining potatoes, 1 at a time, in the same manner.
• Cover the layered potatoes with foil, weight them with an ovenproof saucepan, and cook them over moderate heat for 5 minutes from the time the butter sizzles.
• Transfer the skillet with the pan weight to the middle of a preheated 425F.
• oven and bake the potatoes for 30 minutes.
• Remove the weight and the foil and bake the potatoes, for 10 minutes more, or until they are tender.
• The potatoes may be made 2 hours in advance and kept, covered loosely, at room temperature.
• Reheat the potatoes, covered with the foil, in a preheated 375F.
• oven for 15 minutes.