Fry the onion and garlic gently in the oil and butter for about 10 minutes or until translucent.
Drain and rinse the beans and add to the pan.
Stir in the remaining ingredients and simmer for about 5 minutes.
Mash roughly and serve.
Serve with tortilla chips, thick yoghurt or sour cream, chopped coriander or parsley and a green salad. Guacamole is always a good addition too.Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.