Scrub potato; bake at 425° for 1 hour or until tender. Let potato cool to touch.
Cut potato in half lengthwise; carefully scoop out pulp, leaving 1/4-inch-thick shells. Set shells aside. Place pulp in a small bowl; mash until smooth.
Combine mashed potato, sour cream, and next 3 ingredients, beating until smooth. Stir in chives. Spoon potato mixture evenly into potato shells, and sprinkle evenly with cheese. Place potato shells in a small ungreased baking dish. Bake at 425° for 5 minutes or until cheese melts.