Six thinly sliced, pearly-pink onions are sautéing gently in a skillet on the hob. I’ll be using them to make a proper quiche Lorraine. There’s no point bothering with that recipe unless you’re sure you have onions that will soften to a sweet, melt-in-the-mouth collapse, a requirement that’s lacking in

90 per cent of those that come my way. But, equally, their crunchy juiciness and fruity aroma would work well in salad, where their sweet mildness cohabits peacefully with other flavours

These are the celebrated “oignons de Roscoff”, once the stock-in-trade of the Onion Johnnies, Breton agricultural labourers who cycled from door to door the length and breadth of these isles selling plaited tresses of these rosy-mauve orbs from their handlebars.

Onion Johnnies were once such a welcome sight in autumn. I can still remember, as a child, running out my home in Glasgow to see them. “Look! Look! It’s

the Onion Johnnies!” With their jaunty berets and wind-resistant Breton nautical jerseys, they were so excitingly French. And the fact they only appeared once a year made their visit truly special. We always bought a tress and hung it up for a few weeks, just to admire it.

This onion trade began in the middle of the 19th century. Once the crop was harvested and dried off, agricultural workers set off from Roscoff in the summer and crossed the English Channel at Portsmouth or Plymouth, first on foot and later on bikes. In 1929, there were 1,500 on the road. Today, it’s thought that there are about 20 in the trade.

In 2014, I met a group of Onion Johnnies – young, enthusiastic – at the Abergavenny Food Festival. Apparently these onion vendors had a particular affinity with Wales because the similarities between the Breton and Welsh languages made it easier for them to communicate.

Several Onion Johnnies married and set up business in Scotland, and each still had a run of 500 customers into the 1980s.

And these allium vendors are still a living phenomenon in France. They even have their own museum, La Maison des Johnnies et de l’Oignon de Roscoff, on the outskirts of the titular town. Roscoff’s mauve-pink onions are highly prized in France, where they have been awarded Appellation d’Origine Controlée and Appellation d’Origine Protégée status. Their only competition in cooking terms are the emollient, deeper red Italian onions from Tropea, in Calabria.

Last week, I was delighted when Edinburgh’s unique and wonderful food emporium, Valvona & Crolla, a legend in its own right, received a consignment of this year’s Roscoff onions, and got into the spirit of the product with a bit of beret wearing.

There’s more than a nod to tradition here. Researching these onions, I came across a 1962 photo of Onion Johnnies laying out their tresses in an airy warehouse at Admiralty Street,

in Leith, near the docks, an easy stroll down the road from the Valvona & Crolla shop in Elm Row.

Living conditions were often spartan,

with groups of Onion Johnnies sleeping on straw beds in empty shops. Perhaps the medicinal qualities of the onions they sold and freely consumed made them a particularly hardy breed.

As well as being a good source of

vitamin C, several B vitamins and

beneficial minerals, onions are rich in micronutrients, such as quercetin, which slows down cell damage, and sulphur compounds that research suggests protect against infection, help lower blood pressure, and ease respiratory conditions like bronchitis and asthma.

A bowl of French onion soup could well be just what the doctor ordered, and

Roscoff onions might have an X factor that science has yet to identify.

Slow Food, the organisation that campaigns to protect the world’s culinary heritage, warns that Roscoff onions are slowly disappearing because they are being replaced by modern hybrid varieties better suited to industrial production, that lack their special qualities. But many greengrocers here still sell Roscoff onions, although they’re easy to miss. We’re so used to looking downwards to find run-of-the-mill onions, it’s easy to miss Breton tresses hung up around the shop. Do buy them whenever you get the chance. You won’t be disappointed. Their skins slip off easily, and the only tears they will bring to your eyes will be tears of happiness.