Place the chopped onion and minced garlic in the bottom of your slow cooker. You'll see the onions look translucent and slightly softened after a few minutes of sitting in the warm pot.

In a medium bowl, whisk together the ketchup, apple cider vinegar, Worcestershire sauce, brown sugar, smoked paprika, cumin, onion powder, cayenne (if using), black pepper, and salt. The mixture should be a deep, rich red colour and smell tangy and sweet.

Nestle the chicken thighs into the slow cooker on top of the onions. They should be snug but not crammed – you'll hear a faint sizzle if the pot is already warm.

Pour the sauce mixture evenly over the chicken, then add the chicken stock around the edges. The liquid should nearly cover the chicken, but not submerge it completely – you'll see the tops of the thighs peeking through the dark red sauce.

Cover and cook on LOW for 4-6 hours, or on HIGH for 2-3 hours. After 3 hours on low, the kitchen will smell like a barbecue joint – sweet, smoky, and savoury. The chicken is ready when it shreds easily with two forks; the meat should feel tender and pull apart with minimal resistance.

Using tongs, transfer the cooked chicken to a large bowl. You'll see the meat is moist and glistening, with a dark caramelised colour on the edges. Shred it with two forks – the fibres should separate cleanly and look juicy, not dry.

Skim any excess fat from the surface of the cooking liquid in the slow cooker. You'll notice a thin layer of golden oil floating on top; remove it with a spoon or a fat separator.

Return the shredded chicken to the slow cooker and stir it into the remaining sauce. The chicken will absorb the liquid, turning a uniform, glossy brown. Let it sit for 5 minutes to soak up all the flavour before serving.