Preheat oven to 350 degrees.
Peel and cute potatoes. Place into a large pot with water and bring to a boil. Reduce heat and simmer until potatoes are tender.
While potatoes are cooking, cook bacon in the oven for 15 minutes or until crisp. Remove from oven and chop into small pieces.
Once potatoes are cooked, drain water and then mash with a potato masher. Add in butter, cream cheese, sour cream, garlic, and 2 cups of cheddar cheese. Mix well and add in milk if needed to get desired consistency. Add salt and pepper as desired.
In a greased baking dish, dump in your potato mixture, then top with 1 cup of cheddar cheese, bacon, and chopped scallions. Cover with foil and bake for 15-20 minutes. Remove the foil and bake until cheese is melted and beginning to brown. Serve warm!