Jersey Royals have been in the shops since February, but the ones to buy are those coming on to the market now. The early arrivals grew in greenhouses; the current ones are the first of the outdoor crop, and the tastiest.
My greengrocer sells Jerseys for only a couple of months. By the end of June, they are getting larger and less interesting. It seems that the supermarkets grab most of the new crop coming through then, and supermarket Jerseys are often disappointing. I suspect that refrigerated storerooms and lorries nullify some of the flavour.
That flavour is hard to define: "earthy" is the best I can do. You get a sense of nourishing soil. The texture is waxy - the cells of the potatoes remain coherent when cooked rather than separating as they do in floury varieties. Natural fertiliser from Jersey's cattle and seaweed is reckoned to be the distinctive ingredient.
All of them are descendants, according to island lore, from one, 15-eyed parent. An islander called Hugh de la Haye cut it up and planted it in about 1880; the following spring, he got baby potatoes that were kidney-shaped and delicious. Today, the seed tubers are still hand-selected, arranged upright, and planted on "cotils" (slopes) from the first week of January to mid-April.
The crop is behind this year. The Jersey Royal Company, which is responsible for 85 per cent of the island's output, tells me that everything was going fine until the end of February, when the mild weather had encouraged healthy growth. Then there were storms; and then three nights of frost. By the end of April, the company had distributed only 60 per cent of the allocation normal for the time of year. It expects the overall crop to be reduced, and prices to be higher.
I think it is a shame to mess around with these early Jerseys. Wash them, but do not rub away all the skin. "Earthy" is not necessarily synonymous with unsubtle; you can obscure the flavour by smothering them in sauces, or by assembling them with lots of other ingredients. Roasting, too, can cause them to lose their character. Steaming works well, provided you do not have so many potatoes crowding the pan that they have uneven access to the heat.
When boiling them, it is a good idea to start them (or any other potatoes) in cold water, bring it slowly to a simmer, and cook them gently, without salt. A saline solution and rapid boil may soften and break down the exterior of the potatoes before they are cooked.
A garlicky vinaigrette, in spite of its strength, will complement Jerseys well. You could boil a garlic clove with the potatoes, slip it from its skin, and crush it into some vinegar with salt and pepper. Don't make the sauce too oily: for each part of vinegar, whisk in just two parts of your chosen oil. Cut up the potatoes and toss them in the sauce while still hot.