Scrub and pierce potatoes. Bake at 375° for 1 hour or until tender. When cool enough to handle, cut a thin slice off the top of each potato and discard. Scoop out the pulp, leaving thin shells. , In a large bowl, mash the pulp with butter. Stir in the chives, salt, pepper and enough milk to obtain desired consistency. Spoon into potato shells; sprinkle with paprika. , Place on an ungreased baking sheet. Bake at 375° for 20-30 minutes or until heated through. (Potatoes may be stuffed ahead and refrigerated or frozen. Allow additional time for reheating.)