Jackie and I eat more celery root (aka celeriac) than anyone else in the world. Or at least more than most of our friends: Whenever we serve it, guests' eyes widen as though they were tasting some wondrous botanical specimen newly brought back from the Indies. Starting in mid-summer, when it begins to show up in our local farmers' markets, and right through the winter, it's something we try to keep in the fridge and to eat frequently.
I've written about cooking celeriac a number of times, for example as a standalone first course with mustard sauce; in a quiche-like tart with leeks; and as an almost startling substitute for béchamel or ricotta in lasagne. Boiled in milk, it also makes a grand puree combined with potatoes.
The other day we needed something to accompany sandwiches made with doggy-bag lobster from a generous restaurant dinner. For reasons I can't put my finger on, we didn't feel like potato chips, not that there were any in the house. What was in the house was a small celery root, the first we'd seen in the Union Square Greenmarket this season. Later in the year, they'll be sold without their leafy tops, but for the moment you get the complete plant. The leaves are very strong in flavor, but I employ them in vegetable stocks and sometimes use a few of the leaves as a distinctive herb.
A worthy little salad to share the plate with our sandwiches - one that also makes a lovely light hors d'oeuvre, either on its own or as part of an assortment - is céleri remoulade (or rémoulade: both spellings are used, which is unusual in a language that is attentively policed by a committee). It's something you can buy everywhere in France, from butcher shops to supermarkets to old-time neighborhood bistros, and it couldn't be simpler: it consists of raw julienned celeriac with mustardy mayonnaise and occasionally a spice or two - often pepper and sometimes celery seed just to paint the lily.
For our dinner, I readied some mayonnaise: I'm not shy about using store-bought (Hellmann's is what my mother used, so that's my brand of choice), but on this rainy Sunday afternoon I made my own, using the quick and easy immersion-blender method demonstrated by the food writer J. Kenji López-Alt.
With the mayo made, I peeled a small (10-ounce / 290-gram) celery root, being merciless about removing the rough outer coat and the root fibers. To julienne it, I used a food processor with a 2-mm julienne blade, but I often do this by hand, slicing the celeriac into thin sheets, then cutting a stack of these crosswise into long shreds. This must be done carefully and with a sharp knife: a celery root is a tough knob. A box grater doesn't work quite as well - the vegetable loses some of its chewy crunch when grated - but the medium holes will do the job after a fashion. Immediately, I tossed the celeriac with lemon to keep it from turning brown, then added a third of a cup (80 ml) of mayonnaise and two generous tablespoonsful of Dijon-style mustard. Note that the homemade mayo already had mustard in it, but céleri remoulade should be very mustardy indeed; exactly how mustardy is up to you, and you may wish to start with one tablespoon and add more to taste.
I stirred in a tablespoonful or so of the celeriac leaves, chopped medium-fine, then checked for salt, pepper and mustard and loosened the salad with another squeeze of lemon juice.
Even though it lies around French charcuteries for hours (days?) on end, and even though it will keep reasonably well in the fridge, this is best when made not too long in advance. That having been said, flavor and texture benefit from half an hour at room temperature before serving. Give it one last stir and one last taste before bringing it to the table.
It has a subtle but genuine celery flavor, especially after a 30-minute rest period, and a nearly crisp chew that is nothing like the waterlogged fibrousness of stalk celery. And if you're using store-bought mayo, it takes just four or five minutes to make - and not much longer if you make your own.
