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

In a medium saucepan, combine the heavy cream, whole milk, minced garlic, salt, black pepper, and ground nutmeg. Warm over medium-low heat for about 5 minutes to infuse the flavors, without letting it boil.

Arrange a third of the sliced potatoes evenly in the bottom of the prepared baking dish, overlapping slightly.

Sprinkle one-third of the grated Gruyère cheese over the potato layer and ladle a portion of the warm cream mixture on top.

Repeat the layers two more times with the remaining potatoes, cream, and cheese, finishing with a generous layer of cheese on the very top and dotting with pieces of butter.

Cover the baking dish loosely with aluminum foil and bake for 40 minutes.

Remove the foil and bake for an additional 20 to 25 minutes, or until the potatoes are fork-tender and the top is golden brown and bubbly.

Let the potato bake rest for 10 minutes before slicing and serving to allow the sauce to set.