Peel potatoes and cut them into chunks. Place potato chunks in a large sauce pan and cover with water. Bring to a boil and cook until potatoes are tender and can be easily pierced with a fork (about 10 minutes).
Meanwhile, mince garlic and sauté in butter for 2 minutes, stirring constantly, to avoid burning.
Drain potatoes and return to pan over high heat. Shake pan until you hear the excess water sizzle (cooking off this excess water will help you make fluffier mashed potatoes). Shake, intermittently, and heat for 1 minute.
Turn off flame. To the potatoes, add sautéed garlic, sour cream, and salt & pepper. Mash together. Add milk (about ¼ c., but you may need more) and stir until you get your desired consistency. Serve hot.