Caramel vinegar
Put the sugar, vinegar, star anise and cinnamon in a small saucepan and cook, stirring, over medium heat until the sugar has dissolved. Bring to the boil and simmer for 5 minutes, or until syrupy.
Stir in the chicken stock and simmer for another 5 minutes, or until slightly reduced. Add the orange juice and peel, reduce the heat to low and simmer gently until thick and syrupy. Season to taste.