The leathery skin of a guajilo chile, the mildly hot dried Mexican pepper that flavors this stew, needs to soak until it's soft enough to purée. Serve this stew with cornbread.
Tear off the stems of the dried chiles and shake out the seeds. Heat a large cast-iron or other heavy skillet over medium heat. Toast the chiles in the skillet, pressing them down with tongs and turning once or twice, until they are fragrant and turn a slightly dark shade, 30-60 seconds. Transfer the chiles to a medium bowl. Pour 2 cups of the hot chicken stock over the chiles and set them aside to soak until soft and pliable, about 30 minutes.
Toast the almonds in the skillet over medium heat, stirring frequently, until pale golden brown, 6-8 minutes. Transfer to a plate to cool completely. Add the cumin, oregano, cinnamon, and peppercorns to the skillet and toast the spices over medium heat, sitrring, until fragrant, about 30 seconds. Transfer to a small bowl to cool. Finely grind the almonds with 1 teaspoon of salt in a food processor or blender. Add the chiles and their soaking liquid, along with the toasted spices, raisins, and garlic. Purée to a smooth paste.
Heat 2 tablespoons of the oil in the skillet over medium heat. Add the spice paste and fry, stirring to keep it from burning, until it becomes a shade darker and is very fragrant, about 5 minutes. Remove the skillet from the heat and set aside.
Heat the remaining 2 tablespoons of oil in a heavy large pot over medium heat. Working in batches, brown the pork all over, about 5 minutes. Transfer the meat to a bowl as it browns. Add the onions to the pot and cook, stirring often, until soft, about 5 minutes.
Return the pork and any accumulated juices to the pot. Stir in the spice paste. Add 2 cups of the stock and season with salt and pepper. Bring to a simmer. Cover the pot and simmer the stew over medium-low heat, stirring occasionally, until the pork is tender, 2-3 hours. Add a little more stock to the pot if the stew begins to dry out. Serve the stew garnished with scallions and cilantro.