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 horizontal pocket into the side of each chicken breast, taking care not to cut all the way through. Open each pocket gently.
04 - Generously fill each pocket with the cheese mixture, distributing it evenly. Secure the openings with toothpicks if needed to hold the filling in place.
05 - Season the outside of each stuffed chicken breast generously with salt, freshly ground black pepper, and dried thyme or herbes de Provence.
06 - Heat olive oil in a large ovenproof skillet over medium-high heat. Sear the chicken breasts for 2 to 3 minutes per side until a deep golden crust forms.
07 - Transfer the skillet directly into the preheated oven. Bake for 20 to 25 minutes until the internal temperature reaches 165°F and juices run clear.
08 - Remove from the oven and let the chicken rest for 5 minutes. Remove any toothpicks, then serve hot alongside your choice of accompaniments.