Heat a Dutch oven over high heat and add the oil. Sprinkle the lamb on all sides with salt and pepper. When the oil begins to smoke lightly, use a pair of metal tongs to arrange the lamb in a single layer in the hot oil. Brown the lamb on all sides, 12 to 15 minutes total. Remove the lamb to a medium bowl.
Stir the onions into the grease and sprinkle them lightly with salt. Cook until tender, 5 to 8 minutes. Stir in the carrots, garlic and parsnips. Season with salt and add the brown sugar. Cook until the vegetables become slightly tender, 5 to 8 minutes.
Add the vermouth and cook until all of the liquid cooks out, an additional 5 to 8 minutes. Stir in the beef stock, miso paste and mustard. Add the lamb back into the stew. Cover and place in the center of the oven. Cook until the meat is tender when pierced with the tip of a knife, 2 to 2 1/2 hours.
Use a large spoon to skim any excess fat or impurities from the surface of the sauce. Taste for seasoning. Stir in the vinegar. Allow to rest for 15 minutes, then top with the coarsely ground pepper and parsley. Serve immediately.
This recipe has been updated and may differ from what was originally published or broadcast.