To prepare celeriac, peel it like a potato, rinse and keep in acidulated water until ready to use to prevent it from discolouring. It can be roasted, boiled and mashed, steamed, made into soup or used to flavour stocks. Grate celeriac, blanch for a few minutes in boiling water, then cool and serve as a salad with a vinaigrette, or grate and serve raw with a rémoulade sauce (mayonnaise with Dijon mustard, capers, gherkins, anchovies and herbs).