Pat the meat dry and season on all sides with the salt and pepper. Heat the oil in a large dutch oven over medium-high heat. Working in batches, sear the meat in the hot oil on all sides, turning carefully with tongs, then transfer to a plate.
4-5 pounds chuck roast, 2 pounds bone-in beef short ribs, 2 teaspoons coarse kosher salt, 1 teaspoon black pepper, 1-2 Tablespoons vegetable oil
Add the onion and garlic to the pot. Sear for 2-3 minutes, turning them once or twice to add a little color.
1 large white onion, 1 garlic bulb
Add the beef broth to the pot with the vegetables, along with the seared meat. Add the bay leaves, dried peppers, ancho chili powder, oregano, and cumin. Bring to a boil, then reduce the heat to medium-low and cook for 30 minutes. Skim any foam off the top.
8 cups beef broth, 8 dried guajillo chilis, 2 teaspoons ancho chili powder, 2 teaspoons Mexican oregano, 1 teaspoon ground cumin, 3 bay leaves
Use a slotted spoon or tongs to remove the peppers, onion, and garlic from the pot. Squeeze the cloves of garlic out from the skin of the garlic bulb. Transfer the cooked veggies to a blender or food processor and blend until smooth, adding broth as needed. Strain and press through a fine mesh sieve to remove bits of skin from the peppers, then stir the puree back into the broth with the meat.
Cover and simmer for 3 hours on low to medium-low until meat is tender and falling apart. Remove the bay leaves and discard.
Remove the meat from the broth and shred, discarding the fatty parts and bones from the short ribs. Strain the liquid through a fat separator, saving the grease in a separate bowl. Return the broth to the pot to keep warm until ready to serve.
Meanwhile, pour the grease into a shallow bowl. Heat a large skillet or griddle over medium heat. Dip each corn tortilla into the reserved grease. Place on the hot griddle and top with some of the shredded meat and cheese. Fold the taco over itself like a quesadilla and press down with a spatula to help seal. Fry until crisp and golden-brown on the bottom, about 2-3 minutes, then flip and cook on the other side.
14-16 white corn tortillas, 2-3 cups Monterey Jack, Mozzarella, or Oaxaca cheese
Serve sprinkled with fresh cilantro and diced white onion, with lime wedges on the side and small bowls of the warm broth on the side for dipping and dip the tacos into the broth while eating.
Chopped fresh cilantro, Lime wedges, Diced white onion