Make the marinade by mixing together the sugar, salt, soy sauce and cornflour slurry. Mix in the pork, let marinate for 20 minutes.
Heat a large frying pan with 1 tablespoon oil over high heat. Stir-fry the garlic and shallots until brown. Fry the pork chops until both sides turn brown, about 3-5 minutes. Turn down the heat to medium-low. Cook the pork chops until done, about 3-5 minutes. Set aside.
Heat the same frying pan with 1 tablespoon oil over high heat. Stir-fry onion with some salt until soft, about 3-4 minutes. Add the ketchup, sugar, soy sauce, vinegar and some hot water until the sauce is at the correct consistency. Turn off the heat. Mix this sauce with the pork chops. Garnish with diced spring onions.
Raw slab sugar is also known as brown sugar in pieces. They are sugar blocks made from brown sugar. If unavailable, you can substitute in dark brown soft sugar to taste.
Both raw slab sugar and black vinegar can be purchased at Chinese/Oriental speciality stores.