Cut pork into individual ribs or 1 inch by 1 inch cubes. Season with salt and pepper.

Heat the vegetable oil in a pot large enough to hold all the pork.

Work in batches. Brown the pork. Each batch should be no more than one layer deep with room around individual pieces. One pound per batch is a reasonable starting point. The maillard reaction that comes from browning the pork adds tons of flavour to this dish so take the time here. It's worth it.

Remove each batch as it finishes browning and place in a bowl. You want to catch all the juices. Juices are flavour.

Remove all but 2 Tbsp fat from the pot. Heat over medium heat. Fry the tomatillo salsa for 2 minutes. Stir constantly to scrape up the brown bits on the bottom of the pot. The sauce will darken.

Add the canned, diced chiles and stir. Return the pork and all accumulated juices to the pot. Add the chicken stock (you want enough so the pork is almost covered).

Simmer for 1 hour.

Add the beans, if using, and simmer another 30 minutes.

Add the cilantro and simmer five minutes more.