Preheat the oven to 375°F (190°C).
Grease the baking dish with butter.
Slice the potatoes thinly and evenly.
In a bowl, mix heavy cream, garlic powder, onion powder, salt, pepper, and paprika.
Place half of the potatoes in the dish.
Pour half of the cream mix over the potatoes.
Sprinkle half of the cheddar and Parmesan cheese on top.
Add the rest of the potatoes.
Pour the rest of the cream mix over them.
Evenly spread the remaining cheese over the top layer.
Pour melted butter over the top layer.
Wrap the dish with foil and bake for 45 minutes.
Remove foil and bake for 15 more minutes until golden brown.
Allow it to sit for 10 minutes before enjoying.