pan loosely with foil and bake another 15 minutes or until chicken breasts are done but still moist inside. Remove foil covering from pan; turn broiler on to brown chicken tops, about 2 minutes. Remove pan from oven. Place chicken on heated platter and keep warm; carefully remove foil strips. Meanwhile, remove and discard mirepoix vegetables from roasting pan. Place pan on top of stove. Remove any surface fat and bring to a boil. Add chicken stock and cream and reduce over high heat, stirring until of desired consistency. Taste and adjust seasonings. To serve, garnish chicken breasts with remaining lemon zest and tarragon. Place a little sauce on a heated plate, then place chicken breast on top. Good served with rice-stuffed tomatoes. Serves 4 to 6, depending upon size of chicken breasts. Note: Mirepoix means aromatic vegetables (carrot, celery and onion) chopped and placed in the bottom of a roasting pan). Most of this dish can be prepared in advance.