Fleur de sel

Fleur de sel is the thin crystalline film that forms on the surface of concentrated brine in a salt marsh on still, warm, dry afternoons, skimmed by hand with a long flat wooden rake called a lousse before it sinks and becomes common coarse salt. Because it crystallises at the air-water interface rather than on the clay floor of the pan, fleur de sel stays white, brittle and hollow, carrying trapped air and minute quantities of magnesium chloride, calcium sulphate and potassium from the concentrated seawater. Sodium chloride content sits around 88 percent, against 98 to 99 percent for refined table salt, and the remaining fraction of trace minerals is what gives the crystal its faintly sweet, almost violet-like aroma and its slow dissolution on the tongue. The reference origins are the marshes of Guerande in Loire-Atlantique, whose Mer des Pertuis salt received French IGP protection in 2012, the Ile de Re marshes off La Rochelle, and the Noirmoutier pans further south, all worked since the early Middle Ages by the salt workers known as paludiers. A parallel Portuguese tradition runs through the Algarve, particularly Castro Marim and Tavira, where flor de sal is harvested by the same principles on slightly warmer pans. Fleur de sel is a finishing salt, not a cooking salt: once dissolved in stock or water it surrenders the texture and delicate minerality that justify its price. Its proper home is on caramels, butter, tomatoes, grilled steak, radishes, foie gras and dark chocolate, added at the last possible moment.