Preheat the oven to 375 degrees Fahrenheit. On a baking sheet arrange the cherry tomatoes. Season with fresh thyme, vanilla, olive oil salt and pepper. Bake for 15-20 minutes or until the tomato skins are cracked. Remove from the oven, place into a bowl and set aside.
Turn the oven up to 400 degrees Fahrenheit.
Arrange an area of assembly (covered with parchment paper or plastic wrap to make for an easy clean up) starting with the six butterflied chicken breasts. Spread the pesto on both sides of the chicken breast. Then arrange the cherry tomatoes on one side and top with the fresh mozzarella. Fold the chicken breasts to close them and then wrap with the prosciutto.
In an oven proof skillet (cast iron is my favorite) warm the olive oil and sear the chickens on both sides until they are golden. Deglaze the pan with chicken stock, cover with aluminum foil and place into the oven to finish cooking about 20 minutes or until the internal temperature of the chicken reaches 165 degrees Fahrenheit.