Pour the hot stock over the couscous in a large bowl. Stir in the orange zest then set aside for 10mins to swell the couscous.
Meanwhile heat a griddle pan or the grill. Run lamb steaks with the harissa then brush lightly with the oil. Cook for 3-4 mins per side.
Fluff up the couscous, then stir in the chickpeas, spring onions, coriander and mint. Seaon if you like. Cover the cooked lamb with foil and allow to rest for 2-3 mins. Serve the couscous topped with the lamb.