Preheat your oven to 375°F (190°C).
Using a sharp knife, cut a pocket into the side of each chicken breast, being careful not to cut all the way through.
Stuff each pocket with a slice of mozzarella, a slice of tomato (or a few cherry tomato halves), and 2–3 basil leaves.
Secure the edges with toothpicks or kitchen twine to keep the filling in place.
Brush the outside of each chicken breast with olive oil.
Season with garlic powder, Italian seasoning, salt, and pepper.
Heat a large skillet over medium-high heat. Add a drizzle of olive oil and sear the chicken for 2–3 minutes per side until golden brown.
Transfer the seared chicken breasts to a baking dish and bake for 15–20 minutes, or until the internal temperature reaches 165°F.
Remove the toothpicks or twine, drizzle with balsamic glaze if desired, and serve hot with your favorite side dishes.