01 - Toast the dried guajillo, ancho, and pasilla chiles in a dry skillet over medium heat for 1 to 2 minutes until aromatic. Transfer to a bowl, cover with hot water, and soak for 15 minutes.
02 - In the same skillet, roast the quartered onion, peeled garlic cloves, and halved Roma tomatoes until charred, approximately 8 minutes.
03 - Drain the soaked chiles and place in a blender with the charred onion, garlic, tomatoes, cumin seeds, dried oregano, ground cinnamon, black peppercorns, whole cloves, and 1 cup of beef broth. Blend until smooth.
04 - Place beef chuck roast chunks and bone-in short ribs into the slow cooker. Pour the blended chile sauce over the beef. Add bay leaves, kosher salt, apple cider vinegar, remaining beef broth, and water. Stir gently to combine ingredients evenly.
05 - Cover and cook on low for 8 hours or until the beef is extremely tender and easily shreddable.
06 - Remove beef from the slow cooker, shred using two forks, and discard any bones. Skim fat from the surface of the broth, reserving some for frying tacos. Strain consommé if desired and keep warm.
07 - Heat reserved fat or vegetable oil in a skillet over medium heat. Briefly dip each corn tortilla into the consommé, then place in the skillet. Sprinkle with cheese if using, add shredded beef, and cook until lightly crisped, folding the tortilla in half.
08 - Serve tacos hot, topped with diced white onion, chopped fresh cilantro, and a squeeze of lime wedge. Accompany with a cup of hot consommé for dipping.