01 - Preheat oven to 400°F. Position the rack in the center of the oven.
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 and stir until well blended.
03 - Using a sharp paring knife, slice a horizontal pocket into the thickest side of each chicken breast, cutting about three-quarters of the way through so the breast opens like a book. Be careful not to cut all the way through.
04 - Divide the cheese filling evenly among the four chicken breasts, spooning a generous amount into each pocket. Press gently to close and secure the opening with toothpicks if needed to keep the filling inside during cooking.
05 - Pat the outside of each stuffed chicken breast dry with paper towels. Season all over with salt, freshly cracked black pepper, and dried thyme or herbes de Provence, pressing the seasonings gently into the surface.
06 - Heat the olive oil in a large ovenproof skillet over medium-high heat until the oil shimmers. Carefully place the chicken breasts in the skillet and sear 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, or until the internal temperature of the thickest part of each breast reaches 165°F and the juices run clear when pierced with a knife.
08 - Remove the skillet from the oven and let the chicken rest for 5 minutes to allow the juices to redistribute. Remove any toothpicks, plate the breasts, and serve hot.