Preheat oven to 350 degrees.
Peel, cube and boil potatoes until just fork tender. Drain mash with butter, cream, sour cream and cream cheese. Season with garlic powder, salt & pepper to taste.
Pour into a buttered 2-quart casserole dish. Top with shredded cheddar cheese.
Bake for 30 minutes until heated through and cheese is bubbly.