In a medium container mix onion, Sauternes wine, soy sauce, vegetable oil and mustard powder. Place pork chops in the mixture. Cover and marinate in the refrigerator 8 hours or overnight. Turn pork chops once while marinating.
Prepare barbecue for high heat and lightly oil grate.
Arrange pork chops on the grate and cook 5 to 7 minutes on each side. Top with crushed pineapple and brown sugar before removing from heat. Discard remaining marinade.