Preheat your oven to 400°F (200°C). Lightly grease a baking dish or a cast-iron skillet with cooking spray.

Place the chicken breasts on a cutting board. Using a sharp knife, carefully slice a deep pocket into the side of each chicken breast, being very careful not to cut all the way through to the other side.

In a small bowl, mix the olive oil, Italian seasoning, garlic powder, salt, and black pepper. Rub this seasoning mixture all over the outside and inside the pocket of each chicken breast.

Stuff each chicken breast pocket with 2-3 slices of fresh mozzarella, 2 slices of tomato, and 3-4 fresh basil leaves.

Seal the edges of the pocket shut using 3 to 4 toothpicks per chicken breast to prevent the cheese from melting out completely during baking.

Place the stuffed chicken breasts into the prepared baking dish. Bake uncovered for 25-28 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the cheese is melted and bubbly.

Optional: For a golden crust, turn the oven to broil for the last 2 minutes of baking, watching carefully so the basil doesn't burn.

Remove the chicken from the oven and carefully remove all the toothpicks.

Drizzle generously with balsamic glaze. Serve immediately while the cheese is still hot and stretchy!