01 - Preheat oven to 400°F.
02 - Using a sharp knife, cut a horizontal pocket into each chicken breast without cutting through completely.
03 - Season chicken breasts inside and out with salt and freshly ground black pepper.
04 - Layer slices of fresh mozzarella, tomato, and 4 basil leaves into each chicken pocket. Secure with toothpicks if necessary.
05 - Heat olive oil in an oven-safe skillet over medium-high heat and sear stuffed chicken breasts for 2 to 3 minutes per side until golden brown.
06 - Transfer skillet to preheated oven and bake for 20 to 25 minutes, until chicken is fully cooked and cheese has melted.
07 - While chicken bakes, combine balsamic vinegar and honey in a small saucepan. Simmer over medium heat for 5 to 8 minutes, stirring occasionally, until thick and syrupy. Remove from heat.
08 - Remove toothpicks from chicken breasts. Drizzle balsamic glaze over the stuffed chicken and garnish with extra basil leaves as desired.