- Preheat the oven to gas mark 4-5, 180°C, 350°F.
- Take a lean boned and rolled shoulder joint, remove strings and flatten out the joint.
- Make the Stuffing: Mix together all stuffing ingredients and place in a sausage shape in the centre of the joint along with the leeks and rosemary. Roll up and secure with string. (Any extra stuffing make into balls and cook around the joint - add these to the joint 20-30 minutes before the end of cooking).
- Weigh the joint when stuffed and calculate the cooking time. 25 minutes per 445g/0.5kg plus an extra 25 minutes. Place on a rack in a roasting tin and open roast in preheated oven for calculated cooking time.
- Serve with steamed leeks, roasted new potatoes and mint jelly.