Peel the potatoes and cut into thin slices with the cucumber slicer. Butter a baking dish and layer the potatoes in the dish. Lightly salt, pepper and sprinkle with cheese on each layer, including the last layer. Pour the cream over so that the potatoes are barely covered.
Bake the gratin for 60-70 minutes, after 50 minutes check whether the gratin is too dark, possibly cover with aluminum foil.
Can be modified with onions, leeks or herbs, but the original is best.