1. Open out the lamb and place in a shallow dish. Whizz half the mint leaves, the lemon zest and juice, garlic, ras el hanout, cayenne, yogurt and seasoning in a blender. Pour over the lamb and turn to coat the meat completely. Cover with clingfilm and chill for at least 2 hours but overnight if possible.
2. Preheat the barbecue (or oven to 200⁰C, gas mark 6). Remove the lamb from the marinade and cook on the barbecue for 35–45 minutes, turning occasionally until just cooked through but still pink. Remove the lamb and leave to rest on a warm plate for 10–15 minutes.
3. Prepare the couscous while the lamb is cooking. Heat the olive oil in a non-stick frying pan, add the couscous and stir over a medium heat for 2–3 minutes until golden brown. Stir the harissa into the stock and add to the couscous. Stir over a medium heat for 10–12 minutes until the couscous is tender and all the liquid is absorbed. Transfer to a bowl, stir well and leave to cool to room temperature.
4. Blanch the broad beans in boiling water for 2 minutes until just tender and add with the pomegranate and remaining chopped mint to the couscous. Season and serve with the sliced lamb.