2 tablespoons vegetable oil
1 boneless pork loin roast, trimmed
Kosher salt and freshly ground black pepper
1 medium onion, thickly sliced
2 carrots, thickly sliced
2 stalks celery, thickly, sliced
3 cloves garlic, smashed
3 sprigs fresh thyme
3 sprigs fresh rosemary
4 tablespoons cold unsalted butter
2 apples, such as Cortland or Rome peeled, cored and cut into 8 slices
2 tablespoons apple cider vinegar
2 cups apple cider
2 tablespoons whole grain mustard
Baby red, skin-on mashed potatoes
Preheat the oven to 400 degrees F.
In a large ovenproof skillet heat the olive oil over high heat. Season the pork loin all over generously with pepper. Sear the meat until golden brown on all sides, about 2 to 3 minutes per side. Transfer the meat to a plate and set it aside.
Add the onion, carrot, celery, garlic, herb sprigs, and 2 tablespoons of the butter to the skillet. Stir until the vegetables are browned, about 8 minutes. Stir in the sliced apples, then push the mixture to the sides and set the pork loin in the middle of the skillet along with any collected juices on the plate. Transfer the skillet to the oven and roast the loin until an instant-read thermometer inserted into the center of the meat registers 140 to 150 degrees F, about 30 to 35 minutes. (See Cook's Note.)
Transfer the pork a cutting board and cover it loosely with foil while you make the sauce. Arrange the apples and vegetables on a serving platter and set aside. Remove and discard the herb sprigs. Return the skillet to a high heat and add the vinegar scraping the bottom with a wooden spoon to loosen up any browned bits. Reduce by half then add the cider and reduce by about half again. Pull the skillet from the heat and whisk in the mustard, and the remaining 2 tablespoons of cold butter. Adjust the seasoning with salt and pepper, to taste.
To plate, place some mashed potatoes on the plate. Remove the roast and slice into 1/2-inch thick pieces and arrange over the mashed potatoes. Arrange the apple mixture along the sides of the potatoes. Drizzle sauce over meat, veggies and potatoes, and serve the rest on the side.
Cook's Note: Pork cooked this way will be slightly pink. If desired, cook the pork to 160 degrees F, but be aware that this lean cut will not be as moist at the higher temperature.