Toast the dried guajillo, ancho, and pasilla chiles in a dry skillet over medium heat for 30 seconds per side, just until fragrant. Transfer to a bowl and soak in hot water for 15 minutes.

Blend the soaked chiles, fire-roasted tomatoes, onion, garlic, beef broth, apple cider vinegar, cumin, dried oregano, smoked paprika, and salt until completely smooth. Let the sauce rest briefly while you prep the slow cooker.

Place the beef chuck roast pieces in the slow cooker along with the cinnamon stick and bay leaves. Pour the blended chile sauce over the top, making sure the beef is well covered.

Cook on low for 8–10 hours until the beef is completely fall-apart tender. Keep the lid on during cooking and avoid stirring.

Remove the beef, shred it with two forks, and discard the cinnamon stick and bay leaves. Return shredded beef to the consommé if you want it coated and warm.

Skim fat from the surface of the consommé and reserve it in a separate bowl. Use this fat to dip the tortillas before griddling.

Dip corn tortillas in the reserved consommé fat, then fill with shredded beef and shredded mozzarella or Oaxaca cheese. Fold the tortillas and place on a hot griddle.

Cook the tacos on the griddle until crispy on both sides, flipping carefully once browned. Repeat with the remaining tortillas.

Serve the birria tacos with small cups of warm consommé, diced white onion, and fresh cilantro. Offer extra consommé for dipping as desired.