Pick through the beans to remove any dirt or stones. Place the beans in a large colander and rinse well. Cover with 12 cups of water and let the beans soak overnight.

Drain the beans and place in a stockpot or large clay olla. Add the oil, onion and garlic, and 10 cups of water. Cook over medium-low heat, stirring occasionally, for 1½ to 2 hours.

When the beans are fully cooked, discard the onion and garlic and season with salt, to taste.

Recipe notes

Fast-track method: To avoid the overnight soaking, follow the steps above but instead of soaking, bring the beans to a boil and turn off the heat. Let the beans rest for 1 hour, then continue cooking over medium-low heat for about 1½ to 2 hours.