Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish.
Boil the diced potatoes in salted water until fork-tender, about 12 to 15 minutes, then drain well.
In a large bowl, mash the hot potatoes with the cream cheese, butter, and sour cream until mostly smooth.
Stir in the garlic powder, chives, salt, and black pepper.
Fold in most of the bacon and about 1½ cups of the cheddar cheese, reserving a little of each for the top.
Spread the potato mixture evenly into the prepared baking dish.
Sprinkle the remaining cheddar and reserved bacon over the top.
Bake for 20 to 25 minutes, until hot and bubbly and the cheese is melted.
Let rest for 5 minutes before serving.
Garnish with extra chives if desired.
Leftovers can be refrigerated for up to 3 days.
