Few people would claim that celeriac is a vegetable of great beauty. In the Riverford Farm Cook Book, Guy Watson, whose family runs one of Britain’s biggest and best-known organic box schemes, confesses to “losing several Conservative customers by unwisely comparing its appearance to Iain Duncan Smith’s forehead on a bad day”.

Solid, knobbly and uninspiringly beige it may be, but the loveliness is all on the inside. With its delicate, nutty, celery-like flavour, it is virtually mandatory in French bistros and traiteurs, dressed with mayonnaise alongside grated carrot in vinaigrette for crudités, or served with charcuterie.

It is great in soups, roasted, or mixed with potatoes in a mash. In season (from now through the winter) every French market and supermarket will feature piles of the root vegetable, but here, while it has its firm devotees among serious cooks, it still hasn’t taken what should be its rightful place alongside the likes of parsnips and turnips. “When we started farming at Riverford in 1985, celeriac was pretty much unknown,” says Watson, “and I suppose we still only sell about a quarter of the quantity we do of parsnips. It’s probably marginally behind butternut squash in terms of popularity.”

Why so little appetite for it? “It’s a difficult vegetable to grow in this country,” says Watson, whose team harvests the vegetables by hand. “I know very few people who are successful at cultivating celeriac in gardens, because it needs a long growing season and consistently good conditions; and of course it is a little more time-consuming to prepare.” It’s true that peeling the bumpy surface with a vegetable peeler can be tricky, so it is often easier to use a knife. Also, if you are grating it or cutting it into matchsticks for remoulade, it can take time. But it’s well worth the effort.

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How do you make remoulade? The absolutes are grated or finely chopped celeriac, mixed into mayonnaise and mustard. Beyond that there are various subtle variations. The first debate is whether to keep the celeriac raw or quickly blanch it – literally drop it into a pan of boiling water for a minute, then drain and leave to cool. Most people add lemon juice, seasoning and sometimes chopped parsley to the mix.

Jane Baxter, head chef at Riverford’s Field Kitchen, also adds double cream; Skye Gyngell, chef at Petersham Nurseries Café in Richmond, Surrey, substitutes crème fraîche for mayonnaise, and includes the zest of the lemon. Sometimes you see more elaborate recipes, incorporating garlic or tarragon, and even cornichons (gherkins) and capers. But why complicate things? For me, raw celeriac, a slug of lemon juice and plenty of black pepper are the keys to raising the flavours from tasty to can’t-stop-eating.

Readers’ queries: I read about a potato that has a red, white and blue skin. Where can I find some?

You mean Mr Little’s Yetholm Gypsy, so called because it was developed by the Little brothers in the Borders village of Yetholm, famous for its gypsy population. You can order from Carroll’s Heritage Potatoes (01890 883060; www.heritage-potatoes.co.uk).

If you have a food query, e-mail food.detective@thetimes.co.uk

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