Celeriac is from the celery family and tastes quite similar, but has a slightly nutty, milder and sweeter taste.
To prepare celeriac, peel it like a potato, rinse and keep in acidulated water (with a squeeze of lemon juice or white wine vinegar) 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 vinaigrette, or grate and serve raw with a rémoulade sauce (mayonnaise with Dijon mustard, capers, gherkins, anchovies and herbs).
For cooking, celeriac boils in 20 minutes and roasts in around 40 minutes when cut into rough-shaped chunks.