In a large skillet, saute mushrooms in butter until tender. Remove and keep warm. Sprinkle pork chops with salt and pepper. In the same skillet, brown chops in oil on both sides; drain.
Add marinara sauce; bring to a boil. Reduce heat; simmer, uncovered, for 8-10 minutes or until a meat thermometer reaches 160°, turning once. Layer pork with pepperoni, mushrooms and cheese. Remove from the heat. Cover and let stand for 2-3 minutes or until cheese is melted.