1Toast dried Ancho chiles and dried Guajillo chiles on a dry comal or skillet over medium heat for 1-2 minutes until fragrant. Be careful not to burn them. Remove stems and seeds from the toasted chiles. Place the chiles in a heatproof bowl and cover with hot water, letting them rehydrate for 20 minutes until softened.
2In a blender, combine the rehydrated chiles, garlic cloves, 50g of the white onion, cumin seeds, Mexican oregano, black peppercorns, whole cloves, fine sea salt, and pulque. Blend until a smooth, uniform marinade is formed. If the mixture is too thick, add a small amount of the chile soaking liquid.
3Cut the pork shoulder into large 5-7 cm cubes. Place the pork shoulder in a large bowl and pour the chile marinade over it, ensuring all pieces are well coated. Cover the bowl and refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to meld.
