Build the base. Scatter the chopped onion and smashed garlic across the bottom of the slow cooker insert. They'll act as a trivet so the beef doesn't sit directly against the hot base. You should smell the sharp, clean bite of raw onion and garlic as you go.

Season the beef. Pat the chunks dry with kitchen paper — they should feel tacky rather than wet — then rub them all over with the cumin, oregano, smoked paprika, ground coriander, salt and pepper. The meat will take on a deep rust-red colour from the paprika.

Mix the braising liquid. In a jug or bowl, whisk together the chipotles and their sauce, tomato purée, cider vinegar, lime juice and beef stock until you have a smooth, brick-coloured liquid with a faint smoky aroma.

Assemble and cook. Nestle the seasoned beef on top of the onions, pour the liquid over, and tuck the bay leaves in at the sides. Cover and cook on low for 6–8 hours or on high for 4–5 hours. Around the four-hour mark, the kitchen will smell richly of smoke and warm spice — that's your cue that things are going well.

Check for doneness. The beef is ready when a fork twists through a chunk with almost no resistance and the fibres start separating on their own. If it still feels springy, give it another 45 minutes and check again.

Shred and reduce. Lift the beef out onto a board and pull it apart with two forks — it should fall into soft, glossy strands. While you shred, switch the slow cooker to high, remove the bay leaves, and let the liquid bubble uncovered for 10–15 minutes until it thickens enough to coat the back of a spoon.

Return and coat. Slide the shredded beef back into the reduced sauce and toss until every strand is slick and deeply coloured. Taste and add more salt or lime juice — the brightness should hit you just after the smokiness.

Warm the tortillas and serve. Heat your tortillas in a dry frying pan for about 20 seconds a side until they puff slightly and smell toasted, then fill with beef and your chosen toppings.