Remove the stems from the guajillo and ancho peppers, then shake or scrape out the seeds. Place the dried chiles into a heatproof bowl and cover them completely with very hot or boiling water. Let them soak for about 15 minutes, or until they are very soft and pliable. Drain off the soaking liquid and discard it, then transfer the softened chiles to a food processor. Blend until you have a smooth, deep red chile paste, scraping down the sides as needed.

Place the beef (or lamb) chunks in a large mixing bowl. Spoon the ancho–guajillo paste over the meat and toss thoroughly, making sure every piece is well coated in the rich chile mixture. This helps season the beef all the way through as it cooks.

Heat the olive oil in a large cast iron pan over medium-high heat. When the oil is hot and shimmering, add the chile-coated beef in a single layer, working in batches if necessary so you don’t crowd the pan. Sear the meat for a few minutes per side, just until each piece develops a nicely browned crust. Transfer the browned chunks to the bowl of a slow cooker or crock pot as they are ready.

With the pan still over the heat, pour in a small splash of beef stock (or water or wine) to deglaze. Scrape the bottom of the pan with a wooden spoon to release all the caramelized brown bits stuck there—this is packed with flavour. Pour this liquid, along with the scraped-up bits, into the slow cooker over the seared meat.

Add the chipotles in adobo, the remaining beef stock, apple cider vinegar, lime juice, chopped onion, garlic, Mexican oregano, cumin, bay leaf, and a generous pinch of salt and black pepper to the crock pot. Stir everything together so the liquid and aromatics are evenly distributed around the beef.

Cover with the lid and cook on high for about 4 hours, or on low for 6–8 hours, until the beef is extremely tender. It should pull apart very easily with a fork. Depending on your slow cooker, you may need a little extra time to reach that fork-tender stage.

Once the meat is done, remove the bay leaf and use two forks to shred the beef directly in the cooking juices. Fold the shredded meat through the sauce so it soaks up all the smoky, tangy, chile-infused flavour.

Warm or lightly toast the tortillas in a dry pan, on a griddle, or directly over a low gas flame until soft and pliable with a few charred spots. Pile the shredded barbacoa onto each tortilla, letting some of the juices soak in.

Top the tacos with your choice of garnishes—fresh cilantro, chopped onion, chopped jalapeno, sliced radish, crumbly white cheese, and a good drizzle of hot sauce. Serve immediately and enjoy while everything is hot and juicy.