In a large frying pan, heat oil over medium-high heat. Brown shanks on all sides then transfer to a slow cooker.
Sprinkle in Moroccan seasoning then add shallots, garlic, ginger, cinnamon, star anise, bay leaves and lemon zest.
Combine stock concentrate and hot water and pour in slow cooker to cover shanks. Cover with lid and cook on low heat for 6–8 hours, or on high for 3–4 hours, until meat is almost falling off the bones.
Near the end of cooking, prepare couscous following packet directions.
To make a jus from the cooking liquid, remove shanks and shallots from slow cooker. Cover with foil to keep warm and set aside. Strain cooking liquid into a pot and bring to the boil. Mix cornflour with cold water then add to pot and stir until jus thickens slightly.
Fluff couscous with a fork. Serve shanks and braised shallots on couscous with jus, along with your favourite green vegetables.