Peel and quarter potatoes. Place in boiling water. Cook until tender. Drain, add cream cheese, butter, garlic salt, sour cream, salt, pepper, and mash. Blend together well. Place in casserole dish and cover with plastic wrap. Place in fridge over night. The recipe actually says to leave it there for at least 3 days. I usually cook it the next day. But I might have to test the 3 day to see if it taste different.