Begin by scrubbing the potatoes to remove dirt and debris. Then cut them into 2-inch square and place them into a large stock pot. Pour enough water into the stockpot to cover the potatoes and bring them to a boil. Allow the potatoes to boil until they are very tender, about 20-25 minutes. When the potatoes are soft, drain the water from the pot. Then add in the sour cream, milk, butter, garlic, salt, and pepper and mash until you reach your desired consistency. Serve and enjoy!