Melt butter in a frypan and cook onion until translucent
In a large bowl, combine remaining ingredients except stock. Add cooled onion mix to bowl and gently combine. Add stock slowly, mixing between additions until moist
Place mixture down the centre of the breast and roll up to enclose stuffing. Tie with kitchen string to secure
Baste turkey with some of the melted butter and place in a roasting pan and roast for 45 mins to 1 hour, basting twice with pan drippings
Remove from oven when golden and tested with a skewer and juices run clear. Cover with foil and rest for at least 10 mins prior to serving