Have ready:
Remove the stems and seeds from:
Toast the chiles in a skillet or in the oven; they should soften but not blacken. Transfer them to a bowl and cover with warm water. Place a plate or bowl on top to keep the chiles submerged and let them soak for 20 minutes.
Meanwhile, sprinkle:
with:
Heat in a large soup pot over medium-high heat until shimmering:
Add the pork in batches and brown on all sides. This should take about 20 minutes. Transfer the pork to a plate and drain all but 2 tablespoons of fat from the pot. Add and cook, stirring, until the onion is softened, about 6 minutes:
Add the pork back to the pot along with:
Increase the heat to high. As the mixture heats, drain the soaked chiles and add to a blender, along with:
Puree until the chiles are a smooth paste. Strain the chile mixture through a fine-mesh sieve into the pot with the pork and stir well. Bring to a boil, then reduce the heat to a simmer, partially cover, and cook until the pork is tender, about 1 ½ hours. Discard the bay leaf. Serve with any of the garnishes from Green Posole.