Although I can buy celery root, also called celeriac, in my local supermarket in Connecticut, it doesn’t seem to be as appreciated in the United States as it is in France — a judgment based on the fact that almost every time I buy it at Stop & Shop, someone asks me what it is. It’s a large, bulbous — okay, gnarly — vegetable with a rough exterior. The best ones are unshriveled and fresh smelling; they might be a little moist, and they might even be found in a bin with a little water in it. The flavor is mellower than that of stalk celery, and sweeter too. You can use it in any dish calling for root vegetables; you can puree it and serve in place of mashed potatoes, or mix the puree into mashed potatoes (I love it this way — see the recipe on page 000); and you can even shred it and serve it raw as a salad (just make sure to toss the celery root with a little lemon juice to keep it from darkening). Celery root must be peeled before it’s used, and this is probably what keeps it from reaching the top of the vegetable hit parade. You can use a regular (sharp) vegetable peeler on it or you can do what chefs do: cut a slice off the top and bottom of the root to level it, put it on a cutting board, and, using a sturdy knife, work your way around the root, slicing the skin off from top to bottom. What you lose in celery root (you’ll be cutting away a little of the vegetable with each slice), you’ll make up for in time.