01 - Preheat the oven to 400°F.
02 - Pat chicken breasts dry and cut a deep pocket lengthwise into each, avoiding cutting through completely.
03 - Season both sides and inside pockets of the chicken breasts with kosher salt, black pepper, and garlic powder.
04 - Fill each chicken breast pocket with sliced mozzarella, tomato slices, and 4 basil leaves; secure with toothpicks if necessary.
05 - Heat olive oil in an oven-safe skillet over medium-high heat; sear stuffed chicken breasts 2–3 minutes per side until golden brown.
06 - Transfer the skillet to the oven and bake for 18–22 minutes until internal temperature reaches 165°F.
07 - Combine balsamic vinegar and honey in a small saucepan; bring to a boil, then simmer, stirring frequently for 5–7 minutes until thickened.
08 - Remove chicken from oven; let rest for 5 minutes, then carefully remove toothpicks.
09 - Drizzle the balsamic glaze over the stuffed chicken; garnish with fresh basil leaves and an optional drizzle of olive oil. Serve immediately.