Preheat the oven to 160C/140C fan/gas 3.
Combine brown sugar, mustard powder, smoked paprika, tomato ketchup, red wine vinegar, Worcestershire sauce, salt, and black pepper in a bowl to make a rub.
Rub the pork shoulder with the rub, ensuring it's well-coated.
Heat oil in a Dutch oven pot over medium-high heat.
Brown all sides of the pork in the pot.
Add chopped onion, garlic, and water to the pot.
Cover with a lid and place in the oven for 3-4 hours until tender.
Remove from the oven, let it cool, then shred the pork with a fork.
Boil the remaining liquid until it thickens into a sauce.
Add shredded pork to the sauce and stir until coated.
Serve with desired accompaniments.