Sear the Beef: Pat the beef chunks dry with a paper towel and season generously with salt and pepper. Heat the vegetable oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Sear the beef in batches until deeply browned on all sides, about 5-7 minutes per batch. Do not overcrowd the pan. Set the seared beef aside on a plate.

Toast the Chillies: Reduce the heat to medium. In the same pot, add the destemmed and deseeded guajillo and ancho chillies. Toast them for about 30-60 seconds per side until they become fragrant and slightly pliable. Be very careful not to burn them, or they will turn bitter. Remove the chillies from the pot and set aside.

Sauté the Aromatics: Add the quartered onion, whole garlic cloves, and halved tomatoes to the pot. Cook, stirring occasionally, until they are softened and lightly charred, about 8-10 minutes.

Create the Adobo Sauce: Return the toasted chillies to the pot. Add the oregano, toasted cumin seeds, ground cloves, bay leaves, cinnamon stick, and beef stock. Bring to a simmer and cook for 15 minutes, until the chillies are fully rehydrated and soft.

Blend the Sauce: Carefully transfer the contents of the pot (including the liquid) to a high-powered blender. Add the apple cider vinegar. Remove the bay leaves and cinnamon stick before blending. Blend on high speed until the sauce is completely smooth. This might take 1-2 minutes. What works best for me is to start on low and gradually increase the speed to avoid hot liquid splashing.

Simmer the Birria: Pour the blended sauce back into the Dutch oven through a fine-mesh sieve, pressing on the solids to extract all the liquid. This step gives you a silky-smooth consomé. Return the seared beef to the pot. Bring to a gentle simmer, then reduce the heat to low, cover, and cook for at least 3 hours, or until the beef is fall-apart tender.

Prepare for Tacos: Once cooked, carefully remove the beef from the pot and place it in a large bowl. Shred it using two forks. Skim any excess fat from the surface of the consomé and reserve it in a small bowl. Taste the consomé and season with more salt if needed. Ladle some of the consomé over the shredded beef to keep it moist.

Assemble and Fry the Tacos: Heat a large, non-stick frying pan or griddle over medium heat. Dip a corn tortilla into the reserved fat (or directly into the top of the consomé) to coat it. Place it on the hot pan. Top one half of the tortilla with a generous amount of shredded beef and grated cheese. Cook for 1-2 minutes until the bottom starts to crisp, then fold the other half over.

Finish and Serve: Cook the taco for 2-3 minutes per side, pressing down gently with a spatula, until it's golden brown, crispy, and the cheese is gloriously melty. Repeat with the remaining tortillas. Serve the hot tacos immediately with a small bowl of the warm consomé for dipping, garnished with fresh coriander, diced onion, and a squeeze of lime.