Caprese Grilled Chicken with Balsamic Reduction

balsamic vinegar

boneless skinless chicken breast halves, rested at room temperature 15 minutes

olive oil (, plus more for brushing grill)

garlic (, finely minced)

salt and freshly ground black pepepr

fresh mozzarella (, sliced into 6 slices)

large Roma tomatoes (, sliced)

basil (, chopped)