Combine the ras el hanout, lemon zest, garlic and 2 tbsp olive oil. Season the lamb shanks well. Heat another 2 tbsp olive oil in a large flameproof casserole over a medium-high heat and, once hot, sear the lamb for 4-5 mins until browned all over. Set aside to cool, then rub over the spice paste. Chill for at least 1 hr, or ideally overnight.

Take the lamb shanks out of the fridge and bring to room temperature. Heat the oven to 170C/150C fan/gas 3. Heat the remaining 2 tbsp oil in the casserole dish over a medium-high heat and sizzle the cinnamon sticks, bay leaves, cardamom and cumin briefly. Add the onions, reduce the heat to low and fry for 15-20 mins, stirring frequently until soft but not coloured. Add the lamb shanks and fry briefly for 1 min, then add the barberries, dried limes along with their soaking liquid and the saffron with its soaking liquid, then pour in the chicken stock. Season well. Turn up the heat to high and bring to the boil, cover and transfer to the oven. Cook for 1 hr 45 mins until the lamb is falling off the bone. Once cool, will keep frozen for a month.

Sprinkle with the rosewater if using, then scatter over the parsley and serve with the jewelled rice (see 'goes well with', below).