For stuffing: Heat butter in a large frying pan. Add onion & cook until soft. Place in a large bowl with remaining ingredients, mix well.
Preheat oven to 180°C.
Rinse turkey under cold water, pat dry inside and out with absorbent paper. Fill cavity with loosely with stuffing then tie legs together with kitchen string.
Place turkey onto an oiled wire rack in a large baking dish. Pour the stock into the dish brush turkey with half of the butter, cover dish tightly with foil. Roast for 2 hours, basting every 30 mintues with pan juices.
Uncover turkey, brush with remaining butter. Roast, uncovered for 30 minutes or until turkey is golden and cooked through (i.e. when juices run clear when the thickest part of the thigh is pierced with a skewer). Remove from oven and let stand for 10 minutes before carving.
Meanwhile pour gravy into a small saucepan and bring to a boil, stirring occasionally. Serve with turkey and your favourite roasted vegetables.