Parsnips are narrow at one end and thick at the other. To cut uniform sticks (which will cook at the same rate), slice three inches from the tip of each, and then halve or quarter the thick end. As the pork cooks, it will release its juices into the skillet, flavoring the pieces.
Before marinating, score the fat to allow the flavors to better infuse the meat, and let the loin soak from two to 24 hours, turning two or three times. Chinese five-spice powder is a blend of spices that usually combines cinnamon, star anise, nutmeg, all-spice, and Szechuan peppercorns in equal measure. It imparts a distinctive, pungent flavor and can be found in Asian specialty stores and some supermarkets.