In a large pan, heat the oil and add the onion. Gently fry for 10 minutes, until soft and translucent. Add the mustard seeds, cumin, chilli, ginger, garlic, turmeric and ground coriander. Fry for a couple more minutes.
Add the tomato purée and cook for another minute. Add the veg stock, coconut milk and cinnamon stick.
Bring to the boil, reduce the heat and simmer for 15 minutes. Add the chickpeas, courgettes, tomatoes and continue to cook for 12-15 minutes, until the courgettes are tender.
Remove the cinnamon stick and stir in the fresh coriander, season and serve.