Creating Apple and Brie Stuffed Chicken is straightforward if you follow these simple steps:

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Prepare Chicken: Place the chicken breasts between two sheets of plastic wrap. Gently pound them to an even thickness using a meat mallet or rolling pin.
3. Season Chicken: Rub the chicken breasts with olive oil, garlic powder, salt, and black pepper.
4. Make Filling: In a bowl, combine the diced apples, Brie cheese, chopped spinach, and walnuts (if using). Mix well to combine.
5. Stuff Chicken: Divide the filling among the chicken breasts. Place a generous amount of the apple and Brie mixture in the center of each breast.
6. Secure Filling: Fold the chicken over to encase the filling. Use toothpicks or kitchen twine to secure the edges if necessary.
7. Sear Chicken: Heat a skillet over medium-high heat. Sear the stuffed chicken breasts for 2-3 minutes on each side until golden brown.
8. Bake Chicken: Transfer the seared chicken to a baking dish and bake in the preheated oven for 25-30 minutes or until the chicken is cooked through and the juices run clear.
9. Rest: Remove the chicken from the oven and let it rest for 10-15 minutes before slicing. This helps maintain its juiciness.
10. Garnish and Serve: Slice the chicken and garnish with fresh rosemary before serving.

These steps will guide you in creating this incredible dish effortlessly.