Scrub the potatoes and prick them on both sides with a fork. Lay them on the oven rack and bake them for 1 1/4 hours or until they are soft.
3
Cut the potatoes in half lengthways. Scoop out the middles and mash them with the butter or margarine. Mix the apple and onion into the potato.
4
Put the potato shells in a heatproof dish. Pile the stuffing mixture inside them and make ridges on the tops with a fork. Return the potatoes to the oven for 15 minutes or until the tops are beginning to brown.