Season the pork: Pat the pork chops dry with paper towels. Season both sides with kosher salt and black pepper.
Sear the pork chops: Heat the olive oil in a large, heavy skillet over medium-high heat. Add the pork chops and sear for about 3–4 minutes per side, or until deeply browned. Transfer the pork chops to a plate.
Cook the onion: Reduce the heat to medium. Add the sliced onion to the same skillet and cook for 4–5 minutes, stirring occasionally, until softened and lightly browned.
Add the garlic: Stir in the minced garlic and cook for about 30 seconds, until fragrant.
Deglaze with cider: Pour in the apple cider and scrape the browned bits from the bottom of the skillet with a wooden spoon.
Build the sauce: Add the chicken stock, Dijon mustard, and fresh thyme. If using, add the cinnamon and sliced apple. Stir well to combine.
Braise the pork: Return the pork chops and any accumulated juices to the skillet. Reduce the heat to low, cover, and gently simmer for approximately 10–15 minutes, depending on the thickness of the chops.
Check the temperature: Use an instant-read thermometer inserted into the thickest part of the pork, avoiding the bone. Pork chops should reach 145°F (63°C), followed by at least a 3-minute rest, according to USDA guidance.
Rest the pork: Transfer the cooked pork chops to a clean plate and let them rest for at least 3 minutes.
Finish the sauce: Simmer the cider sauce uncovered for a few minutes if it needs to thicken. Remove the skillet from the heat and whisk in the butter. For a creamy variation, stir in the heavy cream.
Serve: Taste the sauce and adjust the salt, pepper, or Dijon mustard as needed. Spoon the warm apple cider sauce over the pork chops and serve immediately.