Preheat your oven to 375°F (190°C) and lightly butter a 9x13 inch baking dish.

Wash and peel the potatoes, then slice them thinly, about 1/8 inch thick, using a mandoline or a sharp knife.

In a large bowl, combine the heavy cream, minced garlic, salt, and black pepper, mixing well.

Arrange a single layer of sliced potatoes in the prepared baking dish, pour a third of the cream mixture over them, and sprinkle with a third of the grated Gruyere cheese.

Repeat the layering process two more times, ensuring the top layer is evenly covered with cheese.

Cover the baking dish with aluminum foil and bake for 30 minutes, then remove the foil and bake for an additional 15-20 minutes, or until the potatoes are tender and the top is golden brown and bubbly.

Remove from the oven and let it rest for 10 minutes before serving to allow the gratin to set.