2 lbs waxy potatoes (like Yukon gold), peeled and sliced very thin, about 1/8 inch thick
2 cups half and half or milk
1 1/2 cups Gruyere or Swiss cheese, grated
4 tablespoons butter, plus more for greasing dish
1 clove garlic
1/2 teaspoon ground nutmeg
Kosher salt and freshly ground pepper, to taste
Preheat oven to 400°F and liberally grease a casserole dish with butter. (About 8×12-inch works well.) Set aside.
Add cream, garlic, potatoes, and nutmeg to a large pot and season liberally with salt and pepper. Place over medium-high heat and bring to a boil. Let cook about 10 minutes, potatoes will be slightly tender and liquid will have thickened. Adjust seasoning as needed.
Arrange potatoes in baking dish. If making ahead, cover and chill until ready to bake.
When ready to bake, remove foil and top with grated cheese. Bake uncovered until potatoes are tender when pierced with a knife, about 25-30 minutes, longer if chilled. Let sit 5 minutes before serving. Enjoy!