Soak the saffron in a jug containing the hot stock for a few minutes. Meanwhile, heat the olive oil in a large deep-sided frying pan or casserole over a high heat and brown the chicken pieces for 2-3 minutes. You may need to do this in batches so you don’t overcrowd the pan and steam the chicken. Remove the chicken to a plate and add the onion to the pan. Reduce the heat and cook, stirring occasionally, for 5 minutes.
Add the garlic and spices to the pan and cook, stirring, for a further minute. If you’re using a tagine, transfer the onion to the base and add the saffron-infused stock and the browned chicken pieces (if using a casserole, leave the onion in the pan, then add the chicken and stock). Bring to the boil and simmer over a gentle heat, covered, for 40-50 minutes, until the chicken is tender.
Add the lemons and olives and simmer for a further 15 minutes. Season to taste, scatter with the fresh herbs and serve with couscous.
