1.Boil unpeeled potatoes until tender; drain.
2.Cook onion and bacon in heated oiled frying pan until browned.
4.Cut and discard shallow slice from each potato. Scoop two-thirds of potato from each shell; place shells on baking-paper-lined oven tray. Discard half the potato flesh; combine remainder in bowl with bacon mixture, sour cream and cheese.
5.Spoon mixture into shells; top with extra cheese. Grill until cheese browns. Sprinkle with chives.