Braised Duck Legs With Orange Chocolate Sauce

Name: Braised Duck Legs With Orange Chocolate Sauce
Ingredients: 2 x Orange; 8 x duck legs (I used only 4 because they were quite large); 2 tbsp vegetable oil; 4 x Spanish onions, thinly sliced; 4 x cloves garlic, sliced; 2 x leeks, white part only, sliced; 2 x stalks celery, sliced; 1/4 cup chopped fresh thyme; 2 x bay leaves, broken in half; 5 cup rich chicken stock; salt and pepper; 2 cup sugar; 1 1/2 cup fresh orange juice; 1 1/2 cup fresh lime juice; 5 oz extra-bitter chocolate (at least 70% cocoa); 1/4 cup heavy cream; 1 tbsp butter; dash of red wine vinegar, optional