01 - Preheat oven to 400°F (200°C). Position the rack in the center.
02 - In a small mixing bowl, combine the goat cheese, cream cheese if using, chopped basil, chives, minced garlic, and lemon zest. Season lightly with salt and pepper, then blend until smooth and well incorporated.
03 - Using a sharp knife, slice a deep pocket into the side of each chicken breast, taking care not to cut all the way through. Open the pocket gently to create ample space for the filling.
04 - Generously fill each pocket with the cheese mixture, distributing it evenly. Secure the openings with toothpicks if needed to keep the filling contained during cooking.
05 - Season the outside of each stuffed chicken breast generously with salt, freshly ground black pepper, and dried thyme or herbes de Provence, coating all sides evenly.
06 - Heat olive oil in a large ovenproof skillet over medium-high heat. Once the oil shimmers, place the chicken breasts in the skillet and sear for 2 to 3 minutes per side until a golden-brown crust forms.
07 - Transfer the skillet directly into the preheated oven. Bake for 20 to 25 minutes, or until the chicken is cooked through and the internal temperature reaches 165°F. The juices should run clear when pierced.
08 - Remove from the oven and let the chicken rest for 5 minutes to allow the juices to redistribute. Remove any toothpicks and serve hot, accompanied by roasted vegetables or a green salad.