Grill the chicken breasts on high for 6-8 minutes per side until cooked through and then set aside to cool.
Preheat the oven to 400 degrees F.
Place the cherry tomatoes, onion and garlic a sheet tray. Drizzle them with olive oil, salt and pepper and roast for 20-25 minutes until soft, then take out.
Place the chicken breast down on a serving plate and top with the roasted tomatoes, onion and garlic. Drop some mozzarella balls around the plate.
Drizzle the chicken and topping with balsamic vinaigrette and then rip some basil and place it on top as well. Serve right away while hot.