Rub a baking dish first with a clove of garlic, then with butter. Slice the potatoes into very fine slices on a grater, then layer them in the form in three layers. Pepper each layer and add plenty of salt. Finally pour enough cream on the potatoes to cover them.
Top the casserole with fresh nutmeg and a few flakes of butter and cook for about 40 minutes in the oven preheated to 200 degrees. The gratin is good when it is brown. To be on the safe side, after 40 minutes you can stick a fork in the middle of the gratin to check whether the potatoes are soft.