Preheat the oven to 200°C.
Place the goose on a rack in a roasting tin, prick the skin, and season with salt and pepper.
Stuff the cavity with onion and bay leaves, cover legs with foil, and roast for 1 hour.
Drain the fat from the tin and reduce the oven temperature to 180°C.
Roast for another hour, removing the foil halfway through to brown the legs.
Ensure the goose is cooked by checking that the juices from the thigh run clear.
Transfer the goose to a platter and rest, covered, for 30 minutes.
Increase the oven temperature back to 200°C.
Prepare the stock by simmering giblets, vegetables, herbs, and 1 liter of water for 75 minutes.
Fry stuffing onions and apples in goose fat until caramelized, then mix with breadcrumbs, sausage meat, and sage.
Spread stuffing in a greased tin and bake with apple halves for 20 minutes until golden.
Make gravy by whisking flour into roasting juices, then stirring in cider and stock.
Simmer gravy for 5 minutes, strain, and serve alongside the goose and stuffing.