Mix the rub. In a small bowl, stir together the brown sugar, smoked paprika, cumin, garlic granules, onion granules, oregano, cayenne, salt and pepper. It should smell sweet and smoky straight away, with a faint warmth at the back of your nose from the cayenne.

Season the meat. Pat the pork chunks dry with kitchen paper — damp meat steams rather than seasons — then rub the spice mixture over every side. The pieces should look evenly coated in a deep rust-red crust, with no bare patches of pale meat showing.

Build the base. Scatter the sliced onion and chopped garlic across the bottom of the slow cooker insert. Sit the seasoned pork on top in a single layer. If your chunks overlap slightly, that's fine, but don't pile them into a tower.

Whisk the liquid. In a jug, whisk the chicken stock, tomato purée, vinegar and Worcestershire sauce until smooth and glossy, with no streaks of purée left. Pour it around the meat, not over the top — you want to keep that spice crust intact. The liquid should come about a third of the way up the pork.

Cook low and slow. Cover and cook on low for 8 hours. At the 6-hour mark, lift the lid and check: the kitchen should smell rich and slightly sweet, the liquid should be bubbling gently at the edges, and a fork twisted into the thickest piece should meet almost no resistance. If it still fights back, give it another hour.

Shred it. Transfer the pork to a large bowl and rest it for 10 minutes. It should be too hot to handle comfortably but cool enough to touch with fingertips. Pull it apart with two forks — it should fall into soft, fibrous strands with barely any pressure.

Finish the sauce. Skim the fat from the surface of the cooking liquid with a spoon, then stir the barbecue sauce into the juices left in the insert. Taste it: it should be savoury, a little tangy and just sweet enough. Return the shredded pork, toss until every strand is coated, and switch the slow cooker to warm.

Assemble. Pile the pork generously onto the split buns, spoon over a little extra sauce and add your toppings of choice. Serve immediately, while the bread is still soft and the filling is steaming.