Place the oil in the tagine or covered casserole dish and warm gently over a low heat. Add the onions, celery, leek and garlic and cook for 2 minutes. Add all the spices, tomatoes, and vegetables and cook for a further 3 minutes.
Mix the stock with 2 tablespoons of boiling water and add to the tagine.
Lower the heat and simmer for 40-50 minutes.
Add the chickpeas and cook for a further 5 minutes.
Add the fresh herbs and serve from the tagine or casserole dish with brown rice.