Slow-roast lamb shoulder with rosemary and preserved lemon

Method

1. Preheat the oven to 160°C. Score the skin of the lamb with a knife, spacing the score marks about 2 cm apart and cutting about halfway through the fat. Rub lots of salt and pepper all over the lamb.
2. To make the marinade, put the garlic, chopped rosemary, three-quarters of the preserved lemon (save the rest for the gravy) and 2 tablespoons of the olive oil in a bowl and mix well. Using your hands, rub two-thirds of the mixture all over the lamb until well coated. Place a rosemary sprig on top of the lamb, then truss it with kitchen string to form a log.
3. Place the remaining 3 rosemary sprigs in the base of a roasting dish, then spread the remaining marinade in the dish. Sit the lamb, skin side up, on top of the rosemary. Cover with 2 layers of foil, making sure it is tightly sealed so that it becomes a steaming chamber when it cooks. Put the dish in the oven and slow-roast the lamb for 4 hours. Remove the lamb from the oven and transfer to a tray, cover loosely with foil and leave to rest for 10 minutes before carving.
4. Meanwhile, strain the juices in the roasting dish through a fine sieve into a saucepan. Spoon off the excess fat, place the pan over medium heat to warm through, then whisk in the flour and cook for 1 minute. Add the chicken stock and whisk until the flour has dissolved and the gravy has thickened. Add the remaining quarter of preserved lemon to the gravy, stir well and then pour into a serving jug. Cut the lamb into 1.5 cm thick slices and serve the gravy on the side.