Preheat your oven to 375°F (190°C).
Grease the large baking dish with butter to prevent sticking.
In a medium saucepan over medium heat, combine the heavy cream, minced garlic, salt, black pepper, dried thyme, and paprika. Cook until the mixture is just heated through, stirring occasionally.
In a large mixing bowl, combine the sliced potatoes with half of the cheddar and mozzarella cheeses.
Layer half of the potato mixture into the greased baking dish. Pour half of the cream mixture evenly over the potatoes.
Repeat the layers with the remaining potatoes and cream, finishing with the last of the cheese on top.
Cover the baking dish with aluminum foil and bake in the preheated oven for 45 minutes.
Remove the foil and bake for an additional 15 minutes until the top is golden brown and the potatoes are tender when pierced with a fork.
Let the dish cool for about 5 minutes before serving. Garnish with chopped parsley, if desired.