The classic Ligurian recipe is made with local basil (reputed to be some of the sweetest and best), garlic, salt, pine nuts, pecorino cheese and olive oil. However, Italian food being fundamentally regional, there are variations all over the country.

Sometimes Parmesan is favoured, or no garlic. In other regions almonds, cashew nuts and sometimes walnuts might be used instead of pine nuts. Purists may disapprove, but there are also contemporary deviations using other herbs, rocket or a touch of lemon, whose advocates point out that pesto simply comes from the Italian pestare, to pound, and is therefore open to interpretation.

Are pesto and french pistou the same thing?

Although both sauces use similar ingredients, the key difference is that the Provençal pistou doesn’t include nuts.

What makes a good pesto?

Everyone has their own way of making it, using a pestle and mortar or food processor, their own order of adding ingredients, and preference for smooth or chunky, but the end result should be that no one flavour is dominant. However, the taste and freshness of the basil is paramount.

The secret is fresh young leaves which haven’t developed that aniseedy note of older ones, pounded or blitzed as briefly as possible to retain their glorious flavour. Also, you need a light extra-virgin olive oil, rather than a big, fruity or peppery one.

What about ready-made?

Flavours and textures vary dramatically, from shockingly murky, oily and “cooked” to fresh, fragrant, chunky and homemade, such as the pestos from Stark Naked Foods. There’s no mistaking the fervour of founder Victoria Starke, fourth generation of the Starke herb-farming family in Suffolk.

She began creating fresh pesto partly in response to the sorry state of many jarred versions. “I haven’t copied the Italian recipe for basil pesto like for like – it’s more of an English version,” she says, opting for whole pine nuts, a blend of Italian cheeses and lemon juice, the latter just to meet supermarket demand for longevity (it will keep in the fridge for 10 to 12 days).

However, she advocates putting the tub in the freezer. “Then you can scoop out what you need, like ice cream. The pesto isn’t swimming in oil, so you can add more yourself if you want a sauce to drizzle. Herbs are delicate and you shouldn’t obliterate their flavour by heat treating or bulking out with cheap ingredients.”

Where to buy?

Stark Naked Fresh Pesto in nine varieties is available in most Sainsbury’s, Fresh & Wild and Wholefoods, £2.99 for 150g (01379 870010; www.starknakedfoods.co.uk). Tideford Organics’ chunky Hey Pesto! comes in jars in four varieties and tastes of the real thing, £3.75 for 150g at Waitrose (01803 840555; www.tidefordorganics.com).

Readers’ queries

Can you buy special pans for tarte tatin?

Divertimenti has tin-lined copper moulds designed especially, £28.50 from www.divertimenti.co.uk, or call 0870 1295026.

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

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