1. Peel, wash, and cut the potatoes into thin slices (Note: do not wash them AFTER cutting, as the starch is necessary for the correct consistency).
2. Finely chop the garlic.
3. Bring the milk, garlic, salt, pepper, and nutmeg to a boil in a saucepan, then add the potatoes and cook for 10 to 15 minutes, depending on their firmness.
4. Preheat the oven to 180°C (350°F) and butter a gratin dish.
5. Place the drained potatoes in the dish. Cover them with cream, then place small knobs of butter on top.
6. Bake for 50 minutes to 1 hour.