Heat the oil in a large pan over a moderate heat and brown the lamb shanks all over. Remove from the pan and set aside.
Add the onions to the pan and fry for 3-4 minutes until starting to soften. Add the garlic, coriander, cardamom, chilli flakes, cinnamon stick and cloves and continue to fry for a further couple of minutes.
Put the meat in the slow cooker and add the onion and spices. Add the saffron water, bay leaf, tomatoes, chicken stock and pomegranate molasses. Cover and cook on low for 7 hours. Stir through the fresh parsley and season with black pepper.
Serve the lamb on a bed of couscous (optional) and scatter over the pomegranate seeds.