Sear the beef for depth of flavour. Pat the beef dry with kitchen paper — this is crucial for a good sear. Heat the olive oil in a large frying pan over a high heat until it shimmers and begins to smoke slightly. Sear the beef for 3-4 minutes on each side, until a deep, dark brown crust forms. You'll hear a satisfying sizzle, and the kitchen will fill with a rich, meaty aroma. Don't rush this step; the colour is flavour.

Sweat the aromatics. Remove the beef and set it aside on a plate. Lower the heat to medium and add the chopped onions to the pan. Cook for 5-7 minutes, stirring occasionally, until they become soft, translucent, and just begin to catch a little golden colour on the edges. Add the minced garlic and cook for a further minute, until the smell becomes fragrant and sweet, not burnt.

Bloom the spices and chillies. Tear the dried ancho and chipotle chillies into pieces and add them to the pan along with the cumin, smoked paprika, oregano, and black pepper. Stir constantly for 30-60 seconds. You should smell the spices become incredibly aromatic — that's the essential oils releasing. Immediately pour in a splash of the beef stock to stop the spices from burning.

Build the braising liquid. Add the remaining beef stock, tomato purée, and bay leaves to the pan. Stir everything together, scraping the bottom of the pan with a wooden spoon to lift up any delicious browned bits (the fond). Bring the liquid to a gentle simmer. You'll see the colour deepen to a rich, rusty red.

Combine in the slow cooker. Place the seared beef into the slow cooker. Pour the entire hot liquid mixture from the pan over the beef. The liquid should come about halfway up the side of the meat. Add the lime juice. Put the lid on the slow cooker and set it to low.

Cook low and slow. Let it cook for 8 hours on low, or 6 hours on high. Resist the urge to lift the lid frequently. After about 6 hours, you'll be able to smell the deep, savoury chilli and beef aroma filling your house. The meat will be fork-tender, meaning you can easily pierce it with a fork and it will want to fall apart.

Shred the beef. Using tongs, carefully transfer the cooked beef to a large cutting board or bowl. Be gentle, as it will be very tender. Use two forks to shred the beef into bite-sized pieces. You'll notice the meat is incredibly moist and separates into long, juicy strands. Discard any large pieces of fat.

Finish the sauce. Pour the remaining cooking liquid from the slow cooker through a fine-mesh strainer into a jug or saucepan. Discard the solids (the softened chillies, onions, and bay leaves). Return the strained liquid to the slow cooker (or a pan) and bring it to a simmer. Let it bubble for 5-10 minutes until it reduces slightly and becomes a glossy, flavour-packed sauce. Taste it and add salt as needed.

Combine and rest. Return the shredded beef to the slow cooker and pour over enough of the reduced sauce to coat the meat generously. Stir gently to combine. Let it rest in the warm sauce for at least 10 minutes before serving. This resting time allows the meat to reabsorb the juices, making it even more succulent.