Peel and cube the potatoes; place in a saucepan and cover with water. Cook over medium heat until tender; drain. Mash until smooth (do not add milk or butter). Stir in cream cheese, sour cream, chives, onion salt and pepper. Spoon into a greased 1-1/2-qt. baking dish. Dot with butter; sprinkle with paprika if desired. Cover and bake at 350° for 35-40 minutes or until heated through.