Preheat the oven to 200°C.
Heat oil in an ovenproof frying pan and cook lamb for 2 minutes per side.
Mix breadcrumbs, mustard, and parsley in a bowl.
Press the mixture onto the lamb and bake for 5 minutes until cooked.
Let the lamb rest for 4 minutes.
Place parsnips on a tray, drizzle with oil, and roast for 8 minutes.
Drizzle honey and lemon over parsnips, season, and roast for 2 more minutes.
Boil beef stock and port in a saucepan for 5 minutes.
Stir butter into the sauce until melted.
Serve the lamb with parsnips and spoon the port sauce over the top.