Celeriac

Cut off the knobbly top and base, then stand the root on a board and slice away the thick skin with a sharp knife. Put cut pieces straight into water with a squeeze of lemon, or cook them promptly, as the flesh discolours when exposed to air.

Cut into roughly 2 cm cubes, celeriac usually takes 15–20 minutes to boil or steam until tender enough for a knife to pass through. Roast cubes at 200 °C for about 35–45 minutes, turning once, until browned and soft.

Yes. Peel it thoroughly and slice or grate it finely for salads; toss it straight away with lemon juice or vinegar to slow browning. Raw celeriac is crisp and mildly earthy, and is often paired with apple.

Keep an uncut celeriac in the fridge’s vegetable drawer; it can stay in good condition for several weeks. Wrap a cut surface or put the peeled pieces in an airtight container in the fridge, and use them within a few days.

Its earthy, slightly nutty flavour works well with potato, apple, mustard, lemon, parsley and cream. Serve it mashed with potato, roast it alongside other root vegetables, or make the French salad céleri rémoulade with grated celeriac and a mustardy dressing.

For mash or soup, use turnip or a mixture of potato and celery stalk; both give a different, less distinctive flavour. In a raw grated salad, kohlrabi is a good crunchy substitute, though it tastes more peppery and is less earthy.

No: celeriac is a celery variety grown for its swollen root, while celery is grown mainly for its crisp stalks. Celeriac has a stronger, earthier flavour; celery stalk is much lighter, with 14.7 kcal per 100 g compared with 37 kcal in celeriac.

The part you eat is a swollen underground stem base, not an ordinary root. It grows just above and below the soil, which is why celeriac can look knobbly and often has small roots attached.