Preheat the oven to 375 degrees. Grease a 9x13 casserole dish with nonstick cooking spray.

Wash, peel, and dice the potatoes. Place them in a large pot, cover with water, and boil until they become tender.

Drain the potatoes and gently return them to the pot. Carefully mix in butter, cream cheese, sour cream, and milk.

Next, add garlic powder, salt, pepper, 1 ½ cups of shredded cheese, and 1 cup of bacon. Transfer this mixture into your prepared casserole dish.

Sprinkle the remaining cheese and bacon on top of the potatoes. Bake for 25-30 minutes.

After baking, remove the casserole from the oven, garnish with green onions, and serve.