Moist, slowly braised chicken surrounded by intensely-flavored vegetables and presented with a rich but delicately seasoned cream gravy. The restrained use of herbs enhances rather than dominates the natural goodness of the chicken and the root vegetables. If celariac (celery root) is unavailable you can substitute 2 stalks of celery but discard them before serving. Because the flavors are so simple quality is key. Skipping the sherry and substituting dried herbs instead of fresh will be OK, but it won't live up to its full potential.