Skillet Caprese Chicken Casserole for Two

Name: Skillet Caprese Chicken Casserole for Two
Ingredients: 4 ounces whole-wheat penne or rotini; 8 ounces boneless, skinless chicken breasts, trimmed and cut into bite-size pieces; ½ pint grape tomatoes, halved; 4 tablespoons chopped fresh basil, divided; 1 cup plus 2 tablespoons low-sodium chicken broth; ½ cup reduced-fat milk; ¼ cup reduced-fat sour cream; 1 ½ tablespoons all-purpose flour; ½ teaspoon onion powder; ½ teaspoon dry mustard; ⅛ teaspoon salt; ⅛ teaspoon ground pepper; ½ cup shredded mozzarella cheese; Good-quality balsamic vinegar (optional)