How to Make It
Arrange the pork in one or two layers in a wide, heavy, flameproof casserole. Barely cover with water, and season with salt. Cover and cook over moderate heat until almost tender, about 30 minutes. Drain off most of the broth and reserve, adding enough water to make 2 1/2 cups. Continue to cook the pork uncovered until the fat has been rendered and the meat is slightly browned, about 5 minutes longer.
Meanwhile, using a small sharp knife, slit the chiles lengthwise and remove the stems, seeds and veins. Cover with boiling water and set aside to soak for 15 minutes. Drain.
Pour 1/3 cup of the reserved pork broth into a blender. Add the garlic, cinnamon, bay leaf and oregano and blend until smooth. Add the mixture to the pork in the casserole and fry for a few seconds.
Add 1 more cup of the reserved broth and the drained chiles, a few at a time, to the blender and puree. Strain the chiles over the pork through a fine-mesh sieve, pressing to extract as much of the flesh and juice as possible. Fry the pork, scraping the bottom of the pan to prevent sticking, for about 5 minutes longer.
Add the remaining pork broth to the casserole and cook over low heat until the meat is tender and the sauce is thick enough to coat the back of a wooden spoon, about 1 hour. Season with salt. Serve warm.