Place potatoes in a 6-qt. stockpot; add water to cover. Bring to a boil. Reduce heat; cook, uncovered, 10-15 minutes or until tender. Drain potatoes; return to pot and stir over low heat 1 minute to dry., Coarsely mash potatoes, gradually adding butter, sour cream, cheese, seasonings and enough milk to reach desired consistency. Stir in parsley.