How to Make It
Preheat the oven to 325°. In a large skillet, heat 2 tablespoons of the vegetable oil. Add 4 of the lamb shanks, season with salt and pepper and cook over moderate heat until well browned all over, about 10 minutes. Transfer the shanks to a large roasting pan. Repeat with the remaining vegetable oil and shanks. Pour off the fat.
Heat the olive oil in the same skillet. Add the garlic, onions, carrots and celery and cook over moderate heat until softened, about 10 minutes. Add the wine, bring to a boil over moderately high heat and simmer for 3 minutes. Add the tomatoes, stock, orange zest, oregano and 2 tablespoons of the parsley and bring to a boil. Pour the mixture over the lamb and cover with foil. Braise in the oven for about 3 hours, or until the lamb shanks are very tender.
Increase the oven temperature to 350°. Transfer the lamb shanks to a large, deep baking dish, cover with aluminum foil and keep warm. Pour the sauce and vegetables into a large saucepan; discard the strips of orange zest. Simmer the sauce over moderate heat, skimming the surface occasionally, until richly flavored, about 15 minutes. Season with salt and pepper and pour it over the lamb shanks.
Cover the dish of lamb shanks with foil and bake for about 10 minutes, or until they are heated through. Set a lamb shank on each plate and spoon some of the sauce over and alongside. Garnish with the remaining 2 tablespoons of parsley and serve.