Shellfish pleasure: mussels gathered from the beach make the perfect seaside supper / Alamy

Mussels are as cheap as chips – or free if you pick your own – yet they still send top chefs into ecstasy, discovers Anthea Gerrie.

As evocative of beach holidays as buckets and spades, deckchairs and straw hats, a pile of shiny blue mussels pouring forth the heady aromas of steaming wine and herbs becomes the food of dreams for seaside suppers once the sun has finally come out.

The bivalves may be cheap as chips – around £4 per kilo, or totally free to those who scrape their own off the rocks – but they inspire paroxysms of ecstasy in chefs for their earthy, yet sumptuous taste. "Pierre Koffmann taught me every chef is a peasant, and showed me how to use the shells as knife and fork," says Tom Kitchin, who gets through a staggering 70 kilos every weekend at his Edinburgh pub The Scran & Scallie.

"I love the whole theatre of cooking mussels – scrubbing off the beards, throwing them in the pan, the drama when you clamp on the lid and lift it off just minutes later to reveal they have all steamed open – but it doesn't stop at the mussels for me. From Guy Savoy, I learnt what mussel liquor can bring to a dish, added to reduced chicken stock to make a sauce for fish with a very particular, earthy flavour. He taught me to make terre et mer, a base that combines mussel liquor with the juice of girolles – simply heaven." At his eponymous Michelin-starred restaurant in Leith, Kitchin serves only Scottish mussels, preferably from the isles. "The tides are so strong there, they really flush the water clean, and, when the shell springs open, the mussels inside are so meaty and fat."

Karol Rzepkowski, who fished mussels on Shetland for 10 years before turning supplier of Scottish seafood and meat to restaurants, is one of the few wholesalers to brand Shetland mussels, which he believes deserve singling out for their taste. "Many wholesalers throw them in with other Scottish mussels, but I know from experience that the deep, clean waters of Shetland produce a meatier mussel with a thinner shell," says Rzepkowski, a director of top-end food suppliers Campbell Brothers.

I can vouch for the taste, having just eaten Shetland's finest at Frankie's, Britain's most northerly fish and chip shop, where, as well as messing about with Thai and Moroccan flavours, the island chippie stunningly melts bacon lardons and blue cheese into the mussel-steaming bath – unusual, but it works.

Classic moules marinières simply involves throwing diced shallots, parsley and garlic into a large saute pan with a little white wine before adding the mussels, scrubbed free of any beards and barnacles (Shetlands are virtually beardless), turning the heat up and clamping on a lid for three minutes, by which time most mussels will have opened, though some varieties need a couple of minutes more.

Those who have fallen for moules à la Normande in Trouville or Honfleur will know how sinfully good it is to add a soupçon of double cream to the strained liquid before serving, while a final whisper of curry powder and a few strands of saffron infused in this creamy cooking liquor produces the golden mouclade also loved by the French.

Reputable suppliers such as Sainsbury's, which has Scottish mussels all year round and has seen a sizeable increase in sales, offer nets of shiny, midnight blue, firmly closed mussels – though any found open after cleaning may close in response to a brisk tap, indicating they are still very much alive. Never cook any open mussels that fail to close when tapped, or consume any mussels that have refused to open after five minutes or so of steam.

MSC certification from the Marine Stewardship Council is displayed by many suppliers and restaurants as a guarantee of both quality and sustainability – though it has to be said that mussels are hardly an endangered species, growing prolifically on tidal seedbeds or a rope in the water.

Although restaurants on the south coast and in northern France will be offering local mussels this summer – local supplies are more reliable than Scottish in the period leading up to September when the freshly spawned mussels have thinner shells and can become damaged in transit – the temptation for holidaymakers is to pick their own off the rocks.

From September, Adam Clark, the executive chef of Cornwall's Scarlet and Bedruthan hotels, will be leading guests on foraging walks to pick mussels and demonstrating how to cook them on a campfire: "Those taken off the beach – for me, not till the end of summer – should be picked from a very low tide point in a clean area, the bigger the better, avoiding any that are loose, cracked or slightly open," he advises.

"If the mussel liquor is to be used after they are steamed open, it should be strained through a muslin to remove any grit. Although they're great to eat simply steamed, I like to take them one step further by removing the mussels from their shells and tossing them with a little wild garlic pesto, lemon juice and grated zest, before packing them back into the shells, drizzling with breadcrumbs and grilling."

Although down the coast at Fifteen, head chef Andy Appleton is also serving saltwater mussels – "I do think the taste of the ocean is what people are looking for here," he says of the Jamie Oliver restaurant overlooking Watergate Bay – elsewhere in the South-west, mussels are being hoiked out of river estuaries. Can a freshwater mussel ever measure up in terms of taste?

Certainly, at Gara Rock in southernmost Devon, Tom White's fricassé of Exe mussels and clams in a delicate cream sauce is to die for, and Ben Wright, who grows mussels in the Helford River for Wright Brothers of Soho, says it's more about the actual site mussels are plucked from than the virtues of ocean versus river.

"For me, the best of both worlds is the bouchot, which is clean, like a rope mussel, but has the hardening and fattening characteristic of an inter-tidal estuary, which provides better concentration of food without the barnacles usually associated with these sites," he explains. "These mussels will often be meatier and more robust, but will require a bit more cooking as they have developed strong adductor muscles to protect themselves from predators."

At Gara Rock, White uses a little diced carrot in his own dish of river mussels – their sweetness proves a surprisingly welcome addition and is also used by Vincent Menager, of the Balcon in St James's, for his own favourite mussel dish: "At home, I make a wonderful soup, combining the cooked mussels with carrots, potatoes and leeks and blending the mussel cooking liquor with cream and saffron."

Those who want to get really fancy could try the trick of Anne Anderson, of the Anderson hotel at Fortrose in the Black Isle district of Scotland, who steams her mussels in Belgian Trappist beer before melting Ullapool smoked cheddar into the liquor.

Cooks on Ile de Ré, off the west coast of France, like to steam mussels over a bed of flaming pine needles for added aroma.

In truth, though, the only essentials are a little white wine of the quality you plan to drink, shallots, garlic and parsley and, whenever possible, a blast of salty sea air to whet the appetite.