Mix thoroughly and reserve for seasoning the chicken.
Preheat oven to 340 degrees. Brown off the garlic lightly in olive oil and place to the side. Then saute your spinach quickly until starts to wilt. Remove from the flame and add to lightly browned garlic. Chill. Slide your fingers in between the skin and the breast meat of the chicken. Neatly slide your spinach and garlic mixture in between the skin and the breast meat. Truss your chicken and lightly sprinkle some of your herb mixture over the top of chicken and rub with olive oil. Bake in a pre-heated 340 degree oven for about 45 minutes.
While the potatoes are still warm add your heated milk, butter, mushrooms, and demi-glace. Mix thoroughly until incorporated.
Recipe courtesy of John Halligan, Regent Wall Street, New York, NY