Heat the oil in a large saute pan over medium-high heat. Add the onion and garlic and cook until soft, 3 to 4 minutes. Add the apple, water and brown sugar and cook until the apples are very soft. Stir in the cinnamon and salt and cook for 1 minute. Remove the mixture from the heat and let cool.
Transfer the mixture to a food processor along with the butter and process until slightly chunky. Scrape into a small bowl, cover and refrigerate for at least 1 hour to allow the flavors to meld. Let come to room temperature before serving.
For the glaze:
Whisk all the glaze ingredients in a small bowl.
For the pork:
Bring the water, apple juice, salt, sugar, onion, peppercorns, mustard seeds, thyme and bay leaves to a simmer in a large stock pot and cook until the sugar and salt is dissolved. Let cool completely. Submerge the roast in the brine by placing a plate on top, cover with plastic and refrigerate for up to 4 hours.
Preheat oven to 425 degrees F.
Remove the pork from the brine, rinse under cold water and pat dry with paper towels. Heat the oil in a large saute pan over high heat. Season the pork on both sides with salt and pepper and cook on both sides until golden brown, about 8 to 10 minutes total. Transfer the pork to a baking sheet, brush with some of the glaze and finish cooking in the oven until cooked to an internal temperature of 150 degrees F on an instant-read thermometer, about 30 to 40 minutes, brushing with the glaze every 10 minutes. Remove from the oven, let rest loosely tented with foil for 10 minutes.
Add the shallots to the saute pan (that the pork was browned in) and cook until soft. Add the whiskey, scraping the bottom of the pan with a wooden spoon and cook until almost completely reduced. Add the chicken broth and brown sugar and bring to a boil and cook until reduced to a sauce consistency. Whisk in the butter, season with salt and pepper and stir in the parsley.
Slice the rack into chops and place on a large plate, drizzle a little of the sauce around the pork chop and top with some of the butter. Garnish with parsley sprigs.