It’s a farmers market cliche that celeriac is good in soup. I hear it when folks inquire as to how to use this fragrant root. But I’ve never quite known what to do with that guidance. Add celeriac to my Campbell’s tomato soup? To a batch of clam chowder? To my ramen? All I’ve ever done has been to substitute celeriac for celery, its close relative. If you can get it trimmed and peeled, this knobby subterranean dwelling plant part is a worthy replacement for its watery, stringy above-ground counterpart, with more carbs and less fiber, and an almost tingly flavor on the tongue. Most celeriac bulbs include a hairy matrix of gnarly roots that radiate from the central orb. Sometimes these snakelike appendages have already been trimmed by the time of purchase; otherwise, cut them off yourself. My friends Steve and Luci grow softball-sized celeriacs that are almost as …