1. Preheat your oven to 375°F (190°C). Line a baking dish with parchment paper.
2. Using a sharp knife, cut a pocket into each chicken breast, being careful not to slice all the way through.
3. Stuff each pocket with slices of brie and a spoonful of cranberries.
4. Secure the opening with toothpicks if needed.
5. In a small bowl, combine olive oil, salt, pepper, and thyme. Brush this mixture over the chicken breasts.
6. Heat a skillet over medium-high heat and sear the chicken for 2-3 minutes on each side until golden brown.
7. Transfer the chicken to the prepared baking dish. Pour chicken broth and balsamic vinegar around the chicken.
8. Bake in the preheated oven for 20-25 minutes, or until the chicken is cooked through and juices run clear.
9. Remove from oven, let it rest for 5 minutes before serving to allow the juices to redistribute.

Remember, like my grandmother always said, trust your senses. The chicken should be golden and juicy, and the aroma should fill your kitchen with warmth and anticipation.