Peel and medium dice the celery root. In a medium sauce pot, add the stock and celery root, butter and cream and cook until tender, about 5 minutes. Transfer to a blender and puree until smooth. Reserve.
In a large saute pan sweat the shallots in the butter until tender, about 3 minutes. Add the chanterelles and sweat for 2 minutes. Add the Brussels sprouts and cook further for 2 more minutes. Deglaze with the Madeira wine, making sure to keep the liquid away from the open flame. Add the pancetta and 2 tablespoons of the chicken jus.
Place the chicken back in the oven and re-heat for 5 minutes. Unseal the pot and add the liquid in the claypot into the large saucepan containing the mushrooms and chicken jus. Reduce to demi-glace consistency. Warm the farro and add butter, cooking to a porridge-like consistency, about 2 minutes more, and finish with parmesan cheese.
Carve the chicken. Plate by making a circle of the celery root puree, placing the farro in the center and adding the mushroom & Brussels sprouts. Place the sliced chicken on top, sauce with the chicken jus, and serve immediately.