Add orange juice, salt, mustard, currant jelly, and orange peel. Cook over medium heat, stirring constantly, until jelly is melted. During cooking drain fat and turn duck once, if possible. Stir remaining sauce into cornstarch and cook over medium heat until sauce thickens, then simmer 1 minute. Pour sauce over duck just before serving.
Duck is very high in fat.
To lower the fat content somewhat, pour the sauce off the meat and refrigerate until fat rises to the top. Skim off the fat and reheat before serving .