Method- combine the water, salt and sugar together and cover the chicken and brine the bird for 1 hour. Mix the butter and zest and generous rub on the chicken. Place on the roasting rack and stuff the bird with rosemary. Cut the Brussel sprouts in half, season with salt and place in the roasting pan then place the bird on top. Roast for 1 hr. or until juices run clear once thigh is skewered. Remove the brussels and drain the roasting juices, add the mustard, juice and reduce to half, add some butter and parsley to finish.