1Toast dried Ancho chiles, dried Guajillo chiles, and dried Pasilla chiles on a dry comal or skillet over medium heat until fragrant, about 30 seconds per side. Remove stems and seeds. Place toasted chiles in a bowl, cover with hot water, and let rehydrate for 20 minutes.
2While chiles rehydrate, roast garlic cloves, white onion (cut into quarters), and Roma tomatoes on the comal until softened and slightly charred.
3Drain the rehydrated chiles, reserving some of the soaking liquid. In a blender, combine the drained chiles, roasted garlic cloves, roasted white onion, roasted Roma tomatoes, apple cider vinegar, Mexican cinnamon stick, cumin seeds, whole black peppercorns, whole cloves, piloncillo, and salt. Add enough of the reserved chile soaking liquid to achieve a smooth, thick sauce. Blend until completely smooth.
