Step 1: Prepare the potatoes
Preheat your oven to 180°C (350°F).
Peel the potatoes and rinse them briefly under cold water to remove any dirt.
Using a mandoline or a very sharp knife, slice the potatoes very thinly, about 1 to 2 mm thick. Do not rinse them after slicing to retain the starch, which helps thicken the sauce.
Place the slices in a large bowl and set aside.
Step 2: Prepare the cream
In a saucepan, combine the whole milk and heavy cream. Add a peeled and lightly crushed garlic clove to infuse its flavor.
Heat over medium heat until the mixture just begins to simmer (do not let it boil). Remove from the heat and let it infuse for 10 minutes.
Remove the garlic clove, season with salt, pepper, and a pinch of nutmeg (if using). Mix well.
Step 3: Assembling the gratin
Rub a gratin dish (approximately 20 x 30 cm) with the second garlic clove, cut in half, to lightly flavor it, then generously butter the dish with 20 g of butter.
Arrange the potato slices in even layers, slightly overlapping them for a neat presentation.
Pour the hot cream and milk mixture over the potatoes, ensuring it almost covers the slices (the liquid should just reach the surface without making the gratin soggy).
Distribute the remaining butter (20 g) in small pieces over the top for a golden crust.
If you are making a gratin, sprinkle lightly with grated Gruyère or Comté cheese.
Step 4: Baking
