01 - Toast the guajillo, ancho, and pasilla chiles in a dry skillet over medium heat for 2 to 3 minutes until fragrant. Transfer to a bowl, cover with hot water, and let stand for 10 minutes until softened.
02 - Combine the softened chiles, quartered onion, garlic cloves, tomatoes, cumin, oregano, thyme, smoked paprika, cinnamon stick, whole cloves, bay leaves, peppercorns, apple cider vinegar, and 1 cup of beef broth in a blender. Process until completely smooth.
03 - Place the beef chuck chunks and short ribs in the slow cooker. Pour the blended sauce over the meat. Add the remaining beef broth and kosher salt. Stir to coat the meat evenly.
04 - Cover and cook on low for 8 hours, or until the beef is fork-tender and easily pulls apart.
05 - Remove the beef from the slow cooker and shred using two forks. Discard any bones. Skim excess fat from the surface of the cooking liquid, then strain the consommé through a fine-mesh sieve and reserve for dipping.
06 - Heat a skillet over medium heat. Lightly dip each corn tortilla in the fat layer from the consommé and place in the skillet. Add shredded beef and cheese if using, fold in half, and cook until golden and crispy on both sides.
07 - Serve the crispy tacos topped with diced white onion, chopped cilantro, and lime wedges. Pass the reserved consommé alongside for dipping.