Put the onions, celery and chopped peppers with the oil in your largest flameproof casserole dish or heavy-based saucepan, and fry gently over a low heat until soft but not coloured.
Drain the jar of peppers over a bowl to catch the juices. Put a quarter of the peppers into a food processor with the chipotle chilli, ancho chilli, vinegar, cocoa, dried spices and herbs. Whizz to a purée, then stir into the softened veg and cook for a few mins.
Add the tomatoes and refried beans with 1 can water and the reserved pepper juice. Simmer for 1 hr until thickened, smoky and the tomato chunks have broken down to a smoother sauce.
Add the black beans and mixed beans along with the remaining roasted peppers, cut into bitesize pieces and take off of the heat.