01 - Preheat oven to 400°F (200°C).
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 stir until well blended.
03 - Using a sharp knife, carefully cut a pocket into the side of each chicken breast, taking care not to slice all the way through.
04 - Generously fill each pocket with the cheese mixture. Secure the openings with toothpicks if necessary to keep the filling enclosed.
05 - Season the outside of each stuffed chicken breast evenly 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 for 2 to 3 minutes per side until a golden crust forms.
07 - Transfer the skillet directly into the preheated oven. Bake for 20 to 25 minutes, or until the chicken is fully cooked through and the juices run clear.
08 - Remove from the oven and let the chicken rest for a few minutes. Remove any toothpicks and serve hot.