01 -
Cut the chicken breasts horizontally to open like a book, keeping one side attached.
02 -
Sprinkle kosher salt, black pepper, and thyme evenly over the inside surfaces of each chicken breast.
03 -
Place a layer of spinach or arugula on one side of each breast, then top each with about 3 slices of green apple and Brie cheese.
04 -
Fold the chicken breasts over to enclose the filling and secure with toothpicks if necessary.
05 -
In a small bowl, mix Dijon mustard with coarse ground mustard and brush half the mixture onto the tops of the chicken breasts.
06 -
Heat olive oil in a large skillet over medium-high heat. Place chicken breasts mustard-side down in the skillet, brush the other side with the remaining mustard mixture, and sear for 3-4 minutes per side until golden brown.
07 -
Cover the skillet, reduce heat to just below medium, and cook for 5-8 minutes until chicken is fully cooked.
08 -
Transfer chicken to plates and drizzle with any remaining pan juices before serving hot.