Preheat oven to 180°C.
Place the potatoes onto the middle shelf of the oven and bake for 45 - 60 minutes, or until tender.
Combine the bacon, onions and sour cream and half of the cheeses in a mixing bowl.
Season mixture with salt and pepper and set aside.
Preheat grill on a medium-high heat.
Cut the cooled potatoes into quarters, ensuring skin remains intact.
Scoop out the flesh, leaving a 5 mm layer of potato.
Place skins onto a baking tray, flesh-side down.
Brush with half the butter.
Grill for 3 - 4 minutes, or until golden.
Brush with remaining butter and grill for a further 3 - 4 minutes.
Spoon the bacon mixture into the hollows of the potato skins.
Top with the remaining cheese and grill for a further 4 - 5 minutes, or until cheese is melted.