Fill the same saucepan ⅔ with water and bring to a boil over high heat.
When the water is boiling carefully add the drained beans. The water should be two-inches over the beans. If there is too much, use a heat proof liquid measuring cup to remove the excess.
Add one quarter of the onion, the garlic, the epazote, and the salt. Do not stir.
Partially cover the pan and bring back to a simmer. Once the mixture is simmering adjust the heat so it doesn't boil over.
After about 15 minutes skim any foam that has collected on top of the broth.
Simmer for a total of 30 to 45 minutes, until the beans are tender and creamy. Do not stir.
Carefully remove the onion, garlic, and epazote.
At this point, you can cool the beans and freeze (see Gr8 Do Ahead Notes). Or let them cool and continue with the next part when ready to serve. If you have extra water, do not drain. You will use this in the next part of the recipe.