Step 1: Prepare the Chicken
1. Preheat Oven: Preheat your oven to 375°F (190°C). Grease a baking dish with cooking spray or a little olive oil.
2. Butterfly Chicken: Place each chicken breast between two sheets of plastic wrap. Use a meat mallet or rolling pin to gently pound the chicken to an even thickness (about 1/2 inch). Carefully butterfly each chicken breast by slicing it horizontally, ensuring not to cut all the way through.

Step 2: Stuff the Chicken
1. Season: Season the inside and outside of each chicken breast with salt and pepper.
2. Add Filling: Spread about 1 tablespoon of cranberry sauce inside each chicken breast. Top with slices of brie cheese and sprinkle with fresh thyme leaves.
3. Seal: Fold the chicken breasts over to enclose the filling. If desired, secure with toothpicks to hold the stuffing in place.

Step 3: Bake the Chicken
1. Heat Olive Oil: In a large skillet, heat the olive oil over medium-high heat. Sear the stuffed chicken breasts for about 3-4 minutes on each side until golden brown.
2. Transfer to Baking Dish: Place the seared chicken breasts in the prepared baking dish. If using, sprinkle breadcrumbs on top for added crunch.
3. Bake: Bake in the preheated oven for 20-25 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (74°C).

Step 4: Serve
1. Drizzle with Balsamic Glaze: Remove the chicken from the oven and let it rest for a few minutes. Drizzle with balsamic glaze if desired.
2. Slice and Enjoy: Slice the stuffed chicken breasts and serve warm. Pair with your favorite side dishes, such as roasted vegetables or a fresh salad.