Peel potatoes and cut into large pieces.  Cover and cook in boiling salted water for 15 to 20 minutes, or until potatoes are tender.  Drain potatoes.  Put potatoes through a ricer or mash in a large mixing bowl until no lumps remain.  Add milk in small amounts, beating after each addition, until desired consistency is reached.  Add butter, 1/4 tsp salt, and pepper, beating until mashed potatoes are light and fluffy.  Yields 6 to 8 servings