1. Preheat your oven to 375°F.

2. Place the chicken breasts on a cutting board. Using a sharp knife, carefully cut a pocket into each chicken breast, being cautious not to cut all the way through.

3. In a mixing bowl, combine the diced apples, brie cheese, and baby spinach leaves. Season the filling with salt, pepper, garlic powder, onion powder, and dried thyme. Mix everything together until well incorporated.

4. Carefully spoon the apple and brie filling into the pockets of the chicken breasts. Use your fingers to gently push the filling in, ensuring it’s evenly distributed.

5. Use toothpicks or kitchen twine to secure the open edges of the chicken breasts, keeping the delicious filling intact during the baking process.

6. Brush the outside of the chicken breasts with a light coating of olive oil. Season with additional salt, pepper, and dried thyme for enhanced flavor.

7. Place the stuffed chicken breasts in a shallow baking dish or on a rimmed baking sheet. Bake in the preheated oven for 30-35 minutes, or until the chicken is cooked through (internal temperature should reach 165°F).

8. Once the chicken is fully cooked, remove it from the oven and let it rest for 5 minutes before serving.