Add oil to a pot on medium heat then add the diced onion, bell peppers, and mushroom and fry everything until the vegetables are soft.
Add the tomato and garlic and cook the mixture for about 1 minute making sure not to burn anything.
Add the rest of the ingredients, stir them through, turn your stove to low, and simmer the beans for another 15-20 minutes or until the liquid has reduced and you are ready to serve them.