Heat the grill. In a large bowl, mix the yogurt and half the harissa with seasoning. Remove 2 tbsp, set aside, then add the lamb to the remainder and marinate while you make the couscous (or overnight).
In a bowl, cover the couscous with the hot stock and add the rest of the harissa. Cover with cling film and leave for 5 mins, then stir in the chickpeas, lemon zest and juice, vinegar, apricots, pomegranate seeds and half the mint.
Transfer the lamb to a baking tray and grill for 2-3 mins each side (pour any cooking juices into the couscous and stir). Serve the lamb with the couscous, reserved yogurt and a scattering of mint.