Boil, steam or microwave potatoes until tender; drain. Cook bacon, onion and garlic in heated oiled frying pan over high heat, stirring, for 3-4 minutes or until browned.
Preheat grill. Cut and discard shallow slice from each potato. Scoop two-thirds of potato flesh from each shell; place shells on a baking-paper-lined oven tray. Discard half the potato flesh. Combine remainder in bowl with bacon mixture, sour cream and half of the cheese.
Spoon mixture into shells; top with remaining cheese. Grill for 5 minutes or until cheese browns. Serve sprinkled with chives.