Preheat oven to 350°F.
In a large oven-proof skillet, melt butter over medium-high heat. Add apple, onion, and celery; sauté just until tender (about 5-7 minutes).
Meanwhile, prepare the stuffing according to the package instructions. Use a fork to gently combine the prepared stuffing with the sauteed apple, onion, and celery mixture. Set aside.
Use a sharp knife to cut a pocket in each pork chop. Be careful not to slice all of the way through. Pat the pork chops dry with a paper towel. Season on both sides with salt and pepper.
Fill each pork chop with about ¼ cup stuffing (or as much stuffing as you can fit inside). Secure with toothpicks.
Wipe out the skillet that you used to sauté the apples and vegetables. Add the oil to the skillet and heat over medium-high heat. When the oil shimmers, add the pork chops to the pan and brown on both sides, about 3 minutes per side. Work in batches, if necessary, so that you don't overcrowd the pan.
Arrange all of the browned pork chops in the oven-safe skillet. If you don't have a big enough skillet to hold all of the chops, or if you don't have an oven-safe skillet, place the browned pork chops on a greased or parchment-lined rimmed baking sheet.
Transfer the skillet (or baking sheet) to the oven. Bake, uncovered, for 20-25 minutes, or until juices run clear and an instant-read meat thermometer registers 145°F. Remove toothpicks before serving, and garnish with fresh herbs if desired.