This is one of those classic French salads that feels like it’s a distant cousin of coleslaw. It’s so popular in France that you can buy the celeriac pre-shredded, but why bother when the fresh stuff is available?
With a very sharp knife or a mandolin, cut the celeriac as thinly as possible, then cut the slices into long matchstick like shreds. Blend the mustard, mayonnaise and parsley, then mix with the celeriac and season to taste. Best served with charcuterie, cold meats and smoked fish.