Add the onion and sauté over medium-high heat until soft, about 5 minutes. Stir in the parsnips and cook until lightly browned, 4 minutes. Pour in the bourbon or calvados and scrape up any brown bits from the bottom of the pan. Add the rosemary, pork and pancetta to the pan and cover with the cider, stock, and vinegar. Bring to a simmer, cover, and cook for 2 hours, stirring once, until the pork is fork tender but not completely falling apart.