Reduce heat to medium. In same skillet, heat oil until hot. Add onion and mushrooms; cook 3 minutes, stirring frequently. Stir in milk and seasoning mix (from Ultimate Hamburger Helper box). Heat to boiling. Return pork chops to skillet; spoon some of the sauce over pork. Reduce heat; cover and simmer 9 to 11 minutes, stirring and turning pork chops occasionally, until pork is no longer pink in center.