Lightly grease a baking sheet or line it with parchment.
Cut a deep pocket horizontally into the thickest part of each chicken breast, being careful not to cut all the way through.
Season the outside of each breast with garlic powder, Italian seasoning, salt, and pepper.
Stuff each pocket with sliced mozzarella, Parmesan, tomato slices, and basil leaves. Sprinkle the filling with garlic powder, Italian seasoning, and salt.
Secure each breast with 2–3 toothpicks to hold the filling in place. Place the stuffed chicken in the prepared baking dish.
Bake for 30 minutes.
Remove the chicken from the oven and top each breast with fresh mozzarella slices, tomato slices, a fresh basil leaf, and a drizzle of balsamic glaze,
Remove the toothpicks. Serve Caprese-stuffed chicken immediately.