2.5 lbs Yukon Gold or Maris Piper potatoes, peeled
2 cups heavy cream
1 cup whole milk
3 cloves garlic, minced
1 teaspoon salt
1/2 teaspoon black pepper
1/4 teaspoon ground nutmeg
2 tablespoons unsalted butter, for greasing the dish
1.5 cups Gruyère cheese, grated
2 sprigs fresh thyme, leaves removed
Instructions
Preheat your oven to 350 degrees Fahrenheit. Lightly grease a large baking dish with the unsalted butter. Using a mandoline or a very sharp knife, slice the peeled potatoes into rounds about an eighth of an inch thick. Try to keep the slices consistent in thickness so they cook at the same rate. Do not soak the slices in water, as the natural starch helps thicken the sauce.
In a medium saucepan, combine the heavy cream, whole milk, minced garlic, salt, pepper, and nutmeg. Place the pan over medium heat and bring it to a gentle simmer. Once it starts to bubble slightly around the edges, remove it from the heat. This step ensures the garlic and nutmeg flavors are evenly distributed throughout the cream before it hits the potatoes.
Arrange a third of the potato slices in the bottom of your prepared baking dish, overlapping them slightly like shingles. Pour a third of the warm cream mixture over the layer and sprinkle with a third of the grated Gruyère cheese and some fresh thyme. Repeat this process for two more layers, ending with a generous topping of cheese and the remaining cream.
Cover the dish tightly with aluminum foil and place it in the center of the oven. Bake for about 45 minutes. After this time, remove the foil and continue baking for another 20 to 30 minutes. The potatoes are ready when they are tender enough to be easily pierced with a knife and the top is a deep golden brown and bubbling. If the top browns too quickly, you can loosely tent the foil back over it.
Remove the dish from the oven and let it rest for at least 10 to 15 minutes before serving. This resting period is crucial because it allows the sauce to thicken and set, making the portions much easier to scoop out without the cream running everywhere.
