Preheat your oven to 350°F (175°C).
In a large pot, bring salted water to a boil. Add the cubed potatoes and cook until tender, about 15-20 minutes. Drain and return to the pot.
Mash the potatoes until smooth. Stir in the heavy cream, melted butter, garlic powder, onion powder, salt, and pepper until well combined.
Fold in the cheddar and Parmesan cheeses until evenly distributed.
Transfer the potato mixture to a greased 9x13-inch baking dish, spreading it out evenly.
Bake in the preheated oven for 25-30 minutes, or until the top is golden and bubbly.
Remove from the oven and let it cool for a few minutes. Garnish with chopped chives before serving.