Preheat oven to 350°F.
Melt butter over medium-high heat in a large ovenproof skillet. Sauté apple, onion, and celery just until tender (about 5-7 minutes).
In the meantime, prepare the stuffing according to the package instructions. Combine the prepared stuffing with the sauteed apple, onion, and celery mixture using a fork. Set aside.
Make a pocket for each pork chop with a sharp knife. Don't slice all the way through. Using a paper towel, pat the pork chops dry. Season salt and pepper on both sides.
Stuff each pork chop with about 1/4 cup of stuffing (or as much as you can fit inside). Use toothpicks to secure.
Clean the skillet that you used to sauté the apples and vegetables. Heat the oil in the skillet over medium-high heat. Add the pork chops to the pan when the oil begins to shimmer and brown them on both sides, about 3 minutes per side. To prevent overcrowding, work in batches if necessary.
In an oven-safe skillet, arrange all of the browned pork chops. Place the browned pork chops on a greased or parchment-lined rimmed baking sheet if you do not have an oven-safe skillet big enough to hold all of the chops.
Place the skillet (or baking sheet) in the oven. Bake for 20-25 minutes, uncovered until juices run clear and an instant-read meat thermometer registers 145°F. Garnish with fresh herbs if desired, and remove the toothpicks before serving.