Directions

1. Preheat oven to 400°F.
2. Heat the vegetable oil in a large ovenproof skillet over high heat. Season the pork generously with salt and pepper. Sear the meat on all sides until golden brown, about 2 -3 minutes per side. Transfer the meat to a plate and set aside.
3. Add the onions, carrots, celery, potato, garlic, herbs and 4 tablespoons of butter to the skillet. Cook and stir the vegetables until brown, about 8 minutes. Add the apples and stir.
4. Push the vegetable-apple mixture to the sides of the pan and set the pork loin in the middle of the skillet along with any juices from the plate. Transfer the skillet to the oven and roast 30 to 35 minutes or until an instant-read thermometer inserted in the center of the meat registers 140° to 150°F.
5. Transfer the pork to a cutting board and tent with foil. Spoon the vegetable-apple mix on a serving platter and set aside. Remove and discard the herb sprigs.
6. Return the skillet to a high heat and add the cider vinegar. Scrap the bottom of the pan with a spoon to loosen up any browned bits. Reduce by half, add the apple cider and reduce by about half again. Remove the skillet from the heat and whisk in the mustard and the remaining 4 tablespoons of butter. Add salt and pepper to taste.
7. Slice the roast into 1/2-inch thick pieces and arrange over vegetable-apple mixture. Drizzle some sauce over the meat. Serve the rest of the sauce on the side.