Preheat your oven to 375°F (190°C).
In a large pot, boil the diced potatoes until tender, about 15 minutes.
Drain the potatoes and return them to the pot.
Add the melted butter, sour cream, milk, garlic powder, onion powder, salt, and pepper.
Mash the mixture until smooth and creamy.
Fold in half of the cheddar cheese.
Transfer the potato mixture to a greased baking dish.
Top with the remaining cheddar cheese and Parmesan cheese.
Bake in the preheated oven for 25-30 minutes until golden and bubbly.
Garnish with fresh herbs before serving.