Cut the onion into quarters and peel the garlic. Heat a dry frying pan over a medium heat and cook the onion, cut-sides down, along with the garlic and whole chillies for a few minutes until deeply charred – you want them to impart a smoky, scorched flavour, but don’t worry about cooking them fully. Tip the charred veg into a food processor.

Toast the cumin seeds in the pan for a few minutes until fragrant, then tip into the food processor with the rest of the dried spices and 1/2 tsp black pepper. Juice the oranges, zest and juice the limes, then pick the oregano leaves (if using fresh). Tip the citrus juices and lime zest, the oregano, chipotle paste, vinegar and sugar into the food processor, season with a good pinch of salt, and blitz until smooth.

Remove any kitchen string from the pork, if it’s tied, and remove the rind (see tip for how to turn this into pork scratchings). Cut the meat into four smaller chunks and transfer to a large container or freezer bag. Pour over the marinade and chill until needed. Will keep chilled for up to two days, or frozen for up to two months. Defrost fully before cooking as directed.

When you’re ready to cook, heat the oven to 150C/130C fan/gas 2. Tip the pork and marinade into an ovenproof dish with a tight-fitting lid (or the bowl of the slow cooker). Cover and cook for 4-6 hrs until the pork is very tender and falling apart, checking every couple of hours and adding a mugful of water if it becomes too dry. (Or, cook for 6-8 hrs on low in a slow cooker – this will produce a lot of liquid by the end of cooking, so if you like, pour the liquid into a pan and simmer over a high heat to reduce into a rich sauce before pouring it back over the pork.)

Shred the pork using two forks, then toss through the sauce in the dish. Serve in buns, wraps or over rice or jacket potatoes, along with your favourite toppings.