Mix the butter, rosemary, pepper and maple syrup together. Stuff the cavity with ½ onion and sprig of rosemary Rub under the skin on each breast.
Then tie up the legs using pitch twine. Pat the chicken dry and make the bacon weave, see instructions (link in recipe).
Drape the bacon weave over the top and stretch it over to the sides. Flip the chicken over and secure the edges with toothpicks. Place in a roasting pan and pour the chicken stock in the pan.
Bake for 1 hour and 15 minutes or until it reaches an internal temperature of 165-170F with a meat thermometer. Remove the chicken from the pan and allow to rest for 10 minutes before cutting into it.
To Make the Sauce
Pour the pan juices into a small saucepan and drain off some of the fat. Cook over medium heat and add in the mascarpone cheese, salt and pepper. Simmer for a few minutes, whisking to combine. Drizzle over the chicken and enjoy!
This is not meant to be a thick gravy, just a thin sauce for extra flavor.