1/2 medium head escarole, torn into bite-size pieces  | 
                                                5 tablespoons olive oil  | 
                                                3 boneless chicken breast halves, skinned  | 
                                                salt and freshly ground pepper  | 
                                                1 large shallot, minced  | 
                                                1/4 cup fresh orange juice  | 
                                                2 tablespoons plus 2 teaspoons balsamic vinegar or red wine vinegar plus 1/4 teaspoon sugar  | 
                                                1 tablespoon grated orange peel  | 
                                                1 1/2 teaspoons dijon mustard  | 
                                                1 7 1/2-ounce can prepared caponata, such as progresso  |