Place the chilis in a saucepan with 3 cups of water and bring it to a full boil on the stove top. Remove the saucepan from the heat and allow the chilis to sit and rehydrate while you’re working on the rest of the recipe.

Transfer the black peppercorns, coriander seed, bay leaves and cinnamon stick to a small skillet and toast over medium-high heat for a couple of minutes. Transfer these spices to a cheesecloth and wrap in kitchen twine to create a removable spice packet. Note: If you have a mortar and pestle, you can crush the spices before making the spice packet. If you’d like, you can also grind the spices using a spice grinder and add them to the sauce directly without making a removable spice packet.

Cut the beef chuck roast into many large chunks and sprinkle all sides with sea salt.

Heat the avocado oil in a large cast iron skillet over high heat until the skillet is sizzling hot (if you have a laser thermometer, wait for the temperature of the skillet to be 400 degrees or above). Sear the chunks of beef on two sides for 3 to 4 minutes, or until a deep golden-brown crust forms. Transfer the chunks of beef to your slow cooker.

Use the same skillet to sauté the onion. Cook the onion over medium-high heat, stirring frequently, until it has softened. Add the garlic, tomato paste, ground cumin and oregano and continue cooking for another 3 minutes or until very fragrant. Transfer this mixture to the crock pot with the seared beef.

Remove any stems from the chilis and transfer the rehydrated chilis WITH the water you used to soak them into the slow cooker, along with the beef stock, apple cider vinegar, and the spice sachet. Give everything a stir and make sure the beef is covered in liquid as much as possible. Secure the lid on your slow cooker and slow cook on low heat for 8 to 10 hours.

Once the slow cooking has finished, remove the meat from the crock pot and transfer it to a cutting board. Use two forks to shred the meat to your desired consistency, then transfer it to a large bowl.

Transfer the chilis to a blender along with 2 cups of the liquid from the crock pot. Blend until completely smooth (note: you can also use an immersion blender to blend all of the braising liquid) Pour this mixture back into the crock pot. This liquid will now serve three purposes: for dipping the corn tortillas prior to frying the tacos, for pouring on the tacos during the frying process, and for serving as dipping sauce.

Heat a large cast iron skillet with a generous amount of avocado oil or canola oil over high heat. Dip corn tortillas in the birria sauce, then transfer them to the hot cast iron skillet. Immediately sprinkle the whole surface of the corn tortilla with desired amount of cheese (if adding). Place the shredded meat on one side of the tortilla, then once the cheese is melted, fold the meat side of the tortilla over, creating a taco.

Drizzle spoonfuls of sauce over the taco, then flip and repeat for the other side. Continue cooking and flipping until the taco reaches your desired level of crisp.

Serve birria tacos with pickled red onions, fresh cilantro, and a bowl or ramekin of the flavorful consommé for dipping the tacos.