Whisk oyster sauce, rice wine, garlic, sugar and water together in a bowl. Add pork chops, coat with the sauce and marinade for half an hour.
Drain the pork chops, add cornflour to the marinade and mix well. Dredge chops in flour mixture and shake off excess.
Add the oil to the non-stick pan over medium-high heat. When the oil is hot, add the pork chops and cook 2 to 2.5 minutes on the each side.
Add the onion slices to the remaining oil and cook until onions are softened and tinged golden, add balsamic vinegar and oyster sauce (one teaspoon). serve with pork chops.