Peel and slice potatoes thinly using a mandoline.
Warm cream, milk, garlic, salt, and pepper in a saucepan.
Grease a baking dish with butter and layer potatoes, cream, and cheese.
Repeat layers until ingredients are used, finishing with cheese.
Cover with foil and bake at 325°F for 2 hours.
Remove foil, bake 30–40 minutes until golden.
Let rest 10–15 minutes before serving.
