01 - Preheat the oven to 400°F. Line a baking tray with parchment paper.
02 - Using a sharp knife, carefully cut a pocket into each chicken breast without slicing through completely.
03 - Season both the exterior and interior of each chicken breast with salt, black pepper, and garlic powder.
04 - Fill each pocket with slices of mozzarella, tomato, and 3 basil leaves.
05 - Use toothpicks to close the openings and hold the filling in place.
06 - Heat olive oil in a large oven-safe skillet over medium-high heat and sear the chicken breasts for 2 to 3 minutes per side until golden brown.
07 - Transfer the skillet to the oven or place the chicken on the prepared baking tray. Bake for 18 to 22 minutes until the chicken is fully cooked and the cheese has melted.
08 - Combine balsamic vinegar and honey in a small saucepan over medium heat. Simmer, stirring occasionally, until reduced by half and syrupy, about 8 to 10 minutes.
09 - Remove toothpicks from the chicken and drizzle with the balsamic reduction before serving.