Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish.
In a saucepan, heat cream, milk, garlic, salt, pepper, and nutmeg over medium heat until warm.
Arrange half of the potato slices in the prepared dish. Pour half of the cream mixture over the potatoes.
Sprinkle with half of the cheddar and Parmesan cheese.
Layer the remaining potatoes on top, pour the remaining cream mixture, and sprinkle with the remaining cheese.
Drizzle melted butter over the top.
Cover with foil and bake for 45 minutes. Remove foil and bake for an additional 15 minutes or until golden and bubbly.
Garnish with fresh parsley before serving.