In a small saucepan, heat the vinegar and honey over medium/high heat (375-450°F/191-232°C). Bring to a boil and then reduce to a simmer, stirring regularly. When it starts to thicken and has reduced by about half (approximately 10 minutes), remove from the heat and set aside.
Season each chicken breast with salt, pepper, and garlic powder to taste. Cut each breast lengthwise, but not all the way, forming a “pita” shape. This is where you will place the mozzarella, basil, and tomato later.
Place the chicken in two large ziplock bags and pour some of the balsamic reduction into each bag, reserving a small amount for garnish. Allow to marinate in the fridge for at least 30 minutes before grilling.
When ready to grill, spray your cooking grid with non-stick spray or brush with canola oil. Stuff each chicken with one slice tomato, 2 leaves basil, and 2 slices fresh mozzarella. Use a toothpick to seal the opening if desired, this will make flipping the chicken easier.
Grill the chicken over medium/high heat, approximately 450°F/232°C, for 5-7 minutes on each side or until chicken is cooked through. This will bed determined based on the thickness of the chicken you picked. When the chicken is white throughout, it’s done!
Place chicken onto the bottom bun and drizzle with a bit more of the reserved balsamic reduction. Top with the top part of the bun. Enjoy!
Makes 4 sandwiches