Carrageen “moss” (actually a seaweed) is one of Ireland’s more unusual natural resources. There are any number of ways to spell its common name: carrageen, carrageenan, carragheen and carragheenan, take your pick. They’re all derived from the Irish word carraigín, which means “moss of the rocks” (though some think that the -án ending is actually an Irish diminutive, which changes the word’s meaning to “little rock” and connects it to a relatively common Irish place name).
Carrageen’s formal name is Chondrus crispus. It’s the product of one of Ireland’s longest-running industries, and a very useful ingredient for the cook… especially one who’s looking for jelling or setting ingredients that don’t involve animal products.
There’s no telling who first noticed that this seaweed produces a thick jellylike substance that will jell up and set whatever liquid it’s introduced to. The discovery may go back to Bronze Age times. But for many, many years, small seaside communities in Ireland eked out their income by gathering the carrageen seaweed from the rocks near their homes, drying and bleaching it (usually in the sun: nowadays the drying is handled in commercial ovens) and then selling it on as a setting agent, cheaper than gelatine and with its own unique, subdued flavor of the sea.
Carrageen has made its way from Ireland all over the world, and can normally be found without too much trouble in health food stores, which sell it with an eye to its natural content of minerals and iron as well as for its natural thickening and demulcent qualities. (It turns up in cough medicines and numerous other preparations for sore throats and troubled chests, as well as in cosmetics and all kinds of food. Numerous dairy products in North America — especially yogurts and sour creams — now routinely contain carrageen as a thickener, instead of being made as they were back in the days when dairy products were given enough time, or allowed a high enough butterfat content, to thicken themselves per maggiori.)
After it’s been processed, the carrageen seaweed retains only the slightest taste or scent of the sea. Some people don’t care for this: others think it adds a unique flavor to a dessert, an edgy, slightly spicy quality. This taste works particularly well with citrus flavors, and treatments including orange, or lemon, or both, are commonplace in Irish cookbooks of the last couple of centuries.
Handling the carrageen itself is quite simple. A brief soaking in warm water activates the frilly, springy seaweed. After that it’s simmered gently for a while with the milk of your choice: these recipes work as well with soy, rice or oat milks as they do with full-cream dairy. Sweetened and flavored — in this case with lemon and orange juice and rind — the thickened mixture is then strained, poured into bowls or molds, and chilled. The final product is a delicate dessert, suitable for having cream poured over it, or a tart fruit sauce.
Carrageen’s “set” tends to be more fragile and delicate than that of commercial gelatines, that being one reason that cooks who know about it seek it out. But if you’re thinking of doing a carrageen dessert in a mold and you really expect it to stand upright, you’ll want to increase the amount of seaweed you use in the cooking by about half.