Heat the oil in a large saucepan and fry the onion and fennel for 5 minutes. Add the stock and harissa and bring to the boil, stir in the couscous and simmer, covered for 5 minutes.
Stir in the sugar snaps and Walnuts and cook for a further 2-3 minutes until the couscous is tender. Add the spinach and chicken and stir until the spinach has wilted.
Spoon into bowls and drizzle with a little chilli sauce to serve.
Cooks tip
Try using pak choi or mange tout instead of the sugar snaps or swap the spinach for shredded Savoy cabbage.