Soak 3 dried guajillo chilies and 2 dried ancho chilies in hot water for 15 minutes. In a blender, mix the soaked chilies with 1 quartered onion, 4 garlic cloves, and 1 (14.5 ounce) can diced tomatoes until smooth.
Place 3 pounds beef chuck roast (cut into large chunks) in the crockpot. Pour the chili mixture over the beef. Add 2 cups beef broth, 2 tablespoons apple cider vinegar, 1 tablespoon dried oregano, 2 teaspoons ground cumin, 2 bay leaves, 1 teaspoon salt, and ½ teaspoon black pepper.
Cook on low for 8-10 hours until beef is tender.
Shred beef and mix with the sauce.
Heat oil in a skillet. Dip tortillas in the top fat layer of the broth from the crock pot, then fry until crispy on both sides.
Fill tortillas with beef mixture, fold, and fry again until crispy.
Serve with additional broth from the crock pot for dipping, cilantro, and onion, if desired. Enjoy!
Notes
You can also cook on High for 5-6 hours, but cooking on LOW is best for more tender meat.Chili selection: If you can't find guajillo or ancho chilies, you can substitute with a combination of dried chipotle and New Mexico chilies for a similar flavor. Refrigerate any leftover beef mixture in an airtight container for up to 5-6 days. You can also store the leftover assembled tacos in an airtight container but they will get soft and less crispy as they store.