Rinse pork chops, pat dry, and season with seasoned salt and pepper. Place them in a 9x13-inch baking dish. Combine onion, mushrooms, and soup in a separate small bowl. Mix together and spoon over chops.
Cover and bake in preheated oven for 45 minutes. Uncover and bake for 15 more minutes. (Note: Time could be less or more depending on thickness of chops.) Pork chops are done with their internal temperature has reached 160 degrees F (70 degrees C).
Pour sauce into a medium pot and bring to a simmer. Whisk together cornstarch and 1/2 cup of sauce in a small bowl. Whisk into pot and simmer until thickened, about 2 minutes longer. Serve with pork chops.