Peel the potatoes, rinse them and cut them into fairly thin slices. Do not wash them after cutting, as this will remove the starch and the gratin will not have any binding effect.
Preheat your oven to 150°C.
Boil milk with 2 crushed garlic cloves, salt, pepper and grated nutmeg.
Add the potatoes to the milk and cook for about ten minutes. Be sure to stir gently from time to time as this mixture tends to stick.
Butter and rub a baking dish with the last clove of garlic. Pour the potatoes (without the milk) inside and sprinkle with cream, place the remaining butter in small pieces on top and bake for 50 minutes to 1 hour.