In a medium bowl, mix together the shredded mozzarella, sun-dried tomatoes, toasted pine nuts, and minced garlic. Season with salt and pepper to taste.
Using a sharp knife, carefully create a pocket in each chicken breast by slicing them horizontally, being cautious not to cut all the way through.
Spoon about 2-3 tablespoons of the mozzarella mixture into each pocket.
Spread a tablespoon of basil pesto on the outside of each stuffed chicken breast, coating evenly.
Heat the olive oil in a large oven-safe skillet over medium-high heat. Once hot, add the stuffed chicken breasts and sear for about 3-4 minutes on each side until golden brown.
Transfer the skillet to the preheated oven and bake for 25-30 minutes, or until the chicken is cooked through and the internal temperature reaches 165°F (74°C).
Remove from the oven and let the chicken rest for 5 minutes. Garnish with fresh basil leaves before serving.
Notes
Let the chicken rest before serving for better flavor.