01 - Preheat the oven to 400°F. Lightly grease a baking dish with olive oil.
02 - Pat chicken breasts dry. Using a sharp knife, cut a horizontal pocket into the thickest side of each breast without cutting through.
03 - Season both inside and outside of the pockets with salt and freshly ground black pepper.
04 - Spoon 1 tablespoon of pesto into each pocket. Add sliced mozzarella and chopped sun-dried tomatoes inside.
05 - Close pockets and secure with toothpicks as needed to keep filling contained.
06 - Place stuffed breasts in the baking dish. Drizzle with olive oil and evenly sprinkle grated Parmesan cheese on top.
07 - Bake for 25 to 30 minutes until the chicken reaches an internal temperature of 165°F and cheese is melted and bubbly.
08 - Remove toothpicks. Let chicken rest for 5 minutes, then slice and serve.