Preheat the oven to 160C, 140C Fan, Gas Mark 3.Place the mutton on a chopping board and make several slits all over the surface with a sharp knife. Season.Line a large non-stick roasting tray with foil, including enough to cover the joint when added.In a small bowl mix together the garlic, ginger, oil and ras el hanout spice mix. Rub the mix all over the joint and transfer to the roasting tray along with the onionsSprinkle the chilli, zest and juice of the lemon and oranges over the joint. Drizzle over the pomegranate molasses.Mix together the stock and tomato pure and pour over the joint.Cover with baking parchment then the foil, and roast in the oven for 4 hours, turning from time to time until the meat falls away from the bone. 20 minutes before the end of the cooking time add couscous or rice, plus barberries or raisins.Remove from the oven, garnish with the herbs, nuts, pomegranate seeds and rose petals (if used).Serve with flatbreads and a selection of salads.