Open one of the butterflied chicken breasts and place between two sheets of plastic wrap or wax paper. Using a heavy pan, preferably cast iron, firmly strike the chicken 5 to 6 times to even out the breast. Repeat with the remaining 3 breasts.
Season both sides of the flattened chicken with salt and pepper. On one-half of the inside of the chicken breast, spread 1/4 cup of mozzarella cheese and 2 basil leaves. Close the chicken breasts by folding over and tuck in any cheese or basil that might have fallen out.
Grill the chicken on a preheated griddle pan on medium-low. Cook the first side for 3-4 minutes uncovered then covered for 3-4 minutes, repeat on the second side.
While chicken is grilling combine all the bruschetta ingredients in a medium bowl.
After plating the chicken, top each breast with 1/2 cup of the bruschetta. Serve immediately and enjoy!