Scrub potatoes. Leave skins on, if desired, or peel thinly and remove eyes. Leave whole or cut into large pieces.
Heat 1 inch water (salted if desired) to boiling; add potatoes and garlic. Cover and heat to boiling; reduce heat. Cook whole potatoes 30 to 35 minutes, potato pieces 20 to 25 minutes or until tender; drain. Shake pan gently over low heat to dry potatoes.
Mash potatoes in medium bowl until no lumps remain. Add milk in small amounts, beating after each addition. (Amount of milk needed to make potatoes smooth and fluffy depends on kind of potatoes used.)
Add butter, salt and pepper. Beat vigorously until potatoes are light and fluffy. If desired, dot with butter or sprinkle with paprika, chopped fresh parsley, watercress or chives.