The beans are soaked for at least 12 hours with a little salt. When making them, put the beans and the chopped carrot in the pot covered with cold water, so that the water exceeds the beans by two fingers.
Proceed to cooking, once it starts to boil, lower the heat and cook for an hour over low heat, taking care that they do not run out of water, aside from frying with the onion and the garlic clove, all finely minced, this fry must be made and add it to the beans when the cooking time has passed, together with the fried onion and garlic add the chopped potato, see if it is necessary to add more water to the beans, add the salt, raise the heat so that it starts to boil and when it starts to boil, lower the heat and let it cook for another half hour, giving the pot a few shakes from time to time to thicken the sauce.
This recipe for jar beans Put the beans in the pot and add a little water and bring it to a boil, add the chopped potato, and the fried onion and garlic (the fried onion must be cooked before add the beans to the pot), add the salt, and let it boil for 15 minutes over medium heat at first and the last 10 minutes over low heat, shaking the pot and taking care that the beans do not stick.
I have put the carrot, because it takes longer to cook than the potato, and if they are cooked for a long time the jar beans fall apart).
