Get butter and sour cream out of refrigerator and allow to come to room temperature.
Peel potatoes and chop into uniform large chunks.
Place in a large saucepan of cold salted water. Bring to a boil and cook for 10-15 minutes or until the potatoes can be easily pierced with a fork or knife.
Drain and return to the pan. Mash potatoes.
Stir in butter, sour cream, chives, garlic powder, salt and pepper. Taste and adjust seasoning to your liking.
Serve topped with additional butter and chives if desired.