Add the brown sugar, rice vinegar, ketchup, water, soy sauce, and cornstarch to a bowl and whisk until the sugar and cornstarch are dissolved. Set the sauce aside.
Season the pork chops with a pinch of salt and pepper on each side.
Preheat a large skillet over medium, or just slightly above medium. Once the skillet is nice and hot, add the cooking oil and swirl to coat the surface. Add the pork chops and cook for about 5 minutes on each side, or until they are nicely browned. Remove the pork chops to a clean plate and cover with a second plate (turned upside down) to keep them warm.
Add the frozen vegetables to the skillet and continue to cook and stir over medium for about two minutes, or just long enough to take some of the ice off (they may still be icy in the center). Give the sauce a brief stir in case any of the cornstarch has settled, then add it to the skillet with the vegetables. Continue to cook and stir until the sauce begins to simmer, at which point it will thicken and go from a cloudy brown to a shiny glaze.
Add the cooked pork chops back to the skillet with the vegetables and sauce. Let the pork chops simmer in the sauce for 2-3 minutes more, or until the internal temperature reaches 145ºF. Serve hot, over rice or noodles.