Spicy bean tacos with all the trimmings
1. Heat the oil in a frying pan over a medium heat. Fry the onion, garlic and celery until soft.
2. Add the mushrooms and chillies and cook for one minute.Add the tomato purée and cook for a further 2-3 minutes. When the mushrooms are soft, add the cocoa powder (if using) and stock and bring to the boil.
3. Reduce the heat and simmer for 15 minutes, then add the beans and cook for a further 10-12 minutes, or until the sauce has reduced and the beans are all heated through.
4. To serve, place 2-3 tablespoonfuls of the bean chilli in each taco shell. Top with the grated cheese, chopped coriander (if using), and a spoon of yoghurt and put on plates.