Preparation

Put the beans in a colander and rinse with cold water. Drain well and place in a large pot. Cover with at least 3 inches of water (about 14 cups). Add the onion and garlic, if using, and bring to a boil. Reduce the heat to medium-low, cover partially, and simmer until the beans are cooked through and soft, 1-1/4 to 1-1/2 hours, depending on the age of the beans.

Add the salt and epazote or cilantro, if using, and cook until the broth has thickened to a soupy consistency and the beans are so soft that they fall apart if you press one between your fingers, about 15 minutes more. If the beans are not quite there, continue to simmer until they are. Add warm water, if necessary, to keep the beans covered with water.

Season to taste with salt. Remove the onion, garlic, and herbs with a slotted spoon before serving. The cooked beans will keep for4 days, tightly covered, in the refrigerator. They also freeze well in their broth.