“A typically French hors d’oeuvre” for Julia Child, and the taste of childhood holidays for me, this creamy, mustardy slaw is a Gallic classic, a stalwart of Parisian bistros and hypermarket chiller cabinets alike. Like many root vegetables, the celeriac may have a face only a mother could love, yet its fresh crunch and sweetly nutty, faintly fennelly flavour makes the perfect base for a winter salad. Next time you’re reaching for a bag of baby leaves, or a tub of coleslaw, give this a whirl instead.The celeriacA celeriac is a celeriac, of course (though it’s sometimes called celery root, it’s actually a different variety cultivated for what’s below, rather than above ground). It can simply be peeled and used as is, but, given the speed at which the exposed flesh discolours, it’s wise to keep it in acidulated water while you work, or soak it in lemon juice, as Anthony Bourdain recommends in the Les Halles Cookbook, in order to keep the pieces looking pearly white.Once peeled, it tends...