Preheat the oven to 375°F (190°C).

Using a sharp knife, create a pocket in each chicken breast by slicing horizontally, being careful not to cut all the way through.

In a bowl, combine the mozzarella, diced tomatoes, chopped basil, and olive oil. Mix well.

Stuff each chicken breast with the mozzarella mixture and secure the openings with toothpicks.

Season the outside of the chicken breasts with salt, pepper, and garlic powder.

In a skillet over medium heat, add a little olive oil and sear the stuffed chicken breasts for about 3-4 minutes on each side until golden brown.

Transfer the chicken to a baking dish and bake in the preheated oven for 20-25 minutes, or until the chicken is cooked through.

Remove the toothpicks, drizzle with balsamic glaze, and serve hot.