Slice the potatoes thinly
Finely chop the onion and garlic
Sauté the onion and garlic in a pan with butter
Place the potatoes, sautéed onion, and garlic in an oven-safe dish
Mix the heavy cream and milk and pour over the mixture
Top with mozzarella cheese and parmesan cheese
Bake in the oven at 180°C for 30 minutes