add potatoes and garlic to a large pot. Fill with water, so the potatoes are completely covered. Bring to a boil and cook for 15-20 min, until the potatoes are fork tender. Drain
Preheat oven to 350 degrees
Mash potatoes. Stir in butter, sour cream, and heavy cream. Mash further if necessary to get to your desired consistency. Season with salt and pepper.
Stir in 1 ½ cups cheese. Add crumbled bacon (reserve some for the topping)
Pour into a 13×9 inch baking dish. Sprinkle with remaining cheese and reserved bacon.
Bake for 20-25 minutes until hot and cheese is melted.
sprinkle with green onions before serving.