To make in a slow cooker
Heat the oil in a large frying pan over a medium heat. Add the onion, carrot and celery. Cook for 8-10 mins, stirring occasionally until soft, then crush in the garlic, tip in the sweet potato chunks and cook for 1 min more. Add all the dried spices, oregano and tomato purée, cook for 1 min, then tip into a slow cooker.
Add the red pepper and chopped tomatoes. Give everything a good stir then cook on low for 5 hrs. Stir in the beans and cook for another 30 mins to 1 hr. Season to taste and serve with lime wedges, guacamole, rice and coriander.