In our house, we have something called “the celery club.” It is a kind of sorority for girls who love celery, something that we invented to convince the littlest chef to try the celery in a stir fry about a year ago. Now that celery is an old friend, we’ve stepped up our celery game with this whimsical and delicious “double celery soup.” Why “double?” you ask. Because the soup is made with both celery root (a type of celery grown primarily for its root, sometimes referred to as “celeriac”) and ubiquitous celery tops or stalks.