Heat the oven to 325 F with a rack in the lower-middle position.
In a large skillet over medium high heat, toast the chilies, pressing with a wide metal spatula and flipping halfway through, about 30 seconds. Transfer to a medium bowl and add the boiling water. Let stand until the chilies are softened, about 20 minutes, then drain.
While the chilies soak, in the same skillet over medium high heat, toast the tortillas, turning frequently, until lightly charred, 2-4 minutes. Transfer to a plate and let cool slightly, then tear into pieces.
In a blender, combine the broth, soaked chilies, torn tortillas and raisins. Puree until smooth, about 1 minute, scraping down the blender as needed.
In a large Dutch Oven over medium high heat, combine the oil and onion. Cook, stirring occasionally, until the onion is lightly browned, 5 minutes. Stir in the garlic, oregano, cumin, and cinnamon, then cook, stirring, until fragrant, around 5 minutes. Add the tomatoes and cook, stirring occasionally, until most of the moisture has evaporated, about 5 minutes. Stir in the chili puree, cocoa powder and pork, then bring to a simmer. Cover, transfer to the oven and cook for 2 hours.
Remove the pot from the oven. Uncover and stir, then return to the oven uncovered. Cook until a skewer inserted into the pork meets no resistance, about 1 hour.
Remove the pot from the oven. Tilt to pool the liquid to one side, then use a wide spoon to skim off and discard fat. Taste and season with salt and pepper.