Heat the oil in a large frying pan, add the onion and sauté over a medium heat for 4 mins. Add the mushrooms and sauté for a further 5 mins until the mushrooms are browned.
Stir in the chick peas, tomatoes, harissa paste and lemon juice. Bring to the boil, cover and simmer for 8 mins. Remove the lid and season to taste.
Mix the lemon zest and parsley together. Serve the mushrooms with couscous and a scattering of the lemon and parsley.