Pork with Black Beans and Chipotle Chiles

Place the sorted and rinsed black beans in a saucepan and add 4 cups of water.
Bring to a boil, then reduce heat to low, cover and simmer for 5 minutes.
Turn off the heat and let soak 30 minutes.
Return the beans to a boil again, then reduce the heat to low, cover, and simmer until the beans are tender and the broth thickens, about 1 hour and 20 minutes.
When the beans are tender, season with salt.
Meanwhile, heat the oil in a wide deep skillet over medium-high heat and brown the pork in batches.
Transfer the meat to a bowl as the pieces are browned.
In the same skillet, cook the onion with 2 tablespoons of water, stirring to scrape up the browned bits from the pan bottom, until softened, 3 to 4 minutes.
Return the meat to the pan, including any collected juices from the bowl.
Add the salt and mix to combine.
Turn off the heat and reserve in the pan.
Put all of the remaining ingredients in a blender, except the reserved beans, and blend until smooth.
Stir the purée into the pork mixture and bring to a boil, then reduce the heat to low, cover, and simmer until the sauce thickens and the meat is tender, about 45 minutes.
Drain off the broth from the beans into a container and save for another use.
Add the drained beans to the pork.
Cook slowly, over low heat, about minutes, to blend for flavors.
Adjust seasoning.