Preheat the oven to 375°F (190°C).
Prepare the stuffing by combining diced apples, Brie, walnuts, thyme, salt, and pepper in a large bowl.
Make a pocket in each chicken breast using a sharp knife.
Stuff each chicken breast with the apple and Brie mixture.
Heat olive oil in a large oven-safe skillet over medium-high heat.
Sear the stuffed chicken breasts for about 4-5 minutes on each side until golden brown.
Add chicken broth to the skillet and transfer it to the preheated oven.
Bake for 25-30 minutes, or until the chicken is cooked through and juices run clear.
Let the chicken rest for 5 minutes before slicing.
Serve warm, garnished with additional thyme if desired.
