Two days ahead, put the beans to soak in cold water overnight.
Next day, drain, cover with fresh water, bring to a simmer and cook gently until really tender. Gently sauté the onions and garlic in olive oil and butter for 10 minutes or so, until golden. Add the ginger and chilli, and cook for a minute or two, then add the drained cooked beans and the passata. Season with salt and pepper and leave overnight for the flavours to develop.
Next day, simmer gently for an hour. Stir in the cocoa or chocolate and garnish with the coriander just before serving.
© 2003 Chantal Coady. All rights reserved.