Place basil, oil, garlic and vinegar in a blender and blend until smooth. Place chicken in a shallow baking dish, add the marinade and turn to coat. Marinate for 2 hours in the refrigerator. Preheat grill. Grill for 4 to 5 minutes on each side or until cooked through.
Using side burners of grill. Heat oil in a medium saucepan over medium high heat. Add the onions and cook until soft. Add eggplant, season with salt and pepper to taste and cook until golden brown. Add celery, tomatoes, olives, capers, pine nuts and raisins and cook for 15 minutes. Stir in vinegar and sugar and cook for 10 minutes longer, season with salt and pepper to taste. Remove from heat and stir in the parsley. Serve at room temperature.
Place 1 sliced chicken breast in the middle of each flat bread. Top with mozzarella, caponata and spinach leaves, roll and serve.