Season the chicken breasts on both sides with salt, dried thyme, and pepper.

Use a sharp knife to slice the chicken breasts nearly in half, creating a pocket for the filling. Set aside.

Add 1 tablespoon of oil to a medium pan over medium heat. Add the shallot and garlic and sauté for 30 seconds. Add the baby spinach and stir for another minute or two, until the spinach begins to wilt.

Add 2 tablespoons of cranberry sauce into each chicken breast. Evenly divide the spinach mixture between the chicken, then top with 1.5 ounces of brie cheese per chicken breast. Use 3 to 4 toothpicks to close the pocket of each chicken breast.

Preheat the oven to 400°F (200°C). Heat 2 tablespoons of olive oil over medium heat in a large oven-safe pan. Sear the chicken for 3 minutes per side, until golden. Transfer the chicken to the oven and continue cooking for 15 to 18 minutes, until the chicken is cooked through to 165°F (73°C).

Remove the chicken from the oven, let it rest for a couple of minutes, then serve with your favorite sides.