Boil the beans with a little water for a few minutes. Change water and put 1.5 liters of water. Chop finely the onion, carrot and celery and add to the beans. After eating a boil reduce the heat to a lesser degree. When the beans beans soften, but not yet cooked, add the chopped pepper, spices and salt. Once the beans are cooked, add the mint and the oil. Turn off the heat but leave the meal on it for 15-20 minutes.