01 - Preheat your 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 stir until well blended.
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 each pocket gently.
04 - Divide the cheese filling evenly among the four chicken breasts, spooning it generously into each pocket. Secure the openings with toothpicks if needed to keep the filling enclosed.
05 - Season the outside of each stuffed chicken breast on all sides with salt, freshly ground black pepper, and dried thyme or herbes de Provence.
06 - Heat the olive oil in a large ovenproof skillet over medium-high heat. Once the oil shimmers, sear the chicken breasts 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 reaches an internal temperature of 165°F and the juices run clear.
08 - Remove from the oven and let the chicken rest for 5 minutes. Remove any toothpicks, then serve hot alongside roasted vegetables or a crisp green salad.