This ancient Eurasian relative of buckwheat and rhubarb grows up looking like spinach—with green arrow-shaped leaves and juicy stems—but is used primarily as a flavoring; though not, in this country, a very popular one. When fresh and tender, sorrel is deliciously sour, packing a green, lemony tartness. Older sorrel tends to bitterness because it develops a high oxalic acid content. Where sorrel is loved, in France, and in northern and eastern Europe, recipes abound for sorrel soup, from classic Potage Germiny to Schav. It also marries beautifully with eggs, and makes a great sauce for fish (it was also once thought that the acids in sorrel sauce dissolved the tiny bones in shad). Don’t be surprised, when cooking sorrel for the first time, at how quickly it melts into a drab-colored puree. Add a chiffonade of leaves after cooking to brighten the color.

The problem for sorrel-lovers is where do you find it? It grows easily enough in the garden, and there are almost 100 species of wild sorrels and docks. But buying it usually means a visit to a well-stocked farmer’s market in late spring and summer. Happily, I found generous, bright green bunches for sale at the Union Square greenmarket last week…

…and then brought them home to make a bracing cold soup.

Chilled Sorrel Soup

This is adapted from a recipe by Gabrielle Hamilton. Thoroughly wash two bunches of sorrel leaves, trimming away the thickest stems. In one small pot, cook a peeled and diced russet potato in a cup of boiling well-salted water until tender. Meanwhile, melt 4 TB of unsalted butter in a 4 quart or larger pot. Dice and cook one medium onion in the butter until translucent. Add the sorrel leaves by the handful, stirring as they melt, until all the sorrel is cooked down. Add half the potatoes and their cooking water to the sorrel (save the other half of the potatoes for a garnish or, if that seems fussy, simply add all of the potatoes to the soup), add another three to four cups chicken stock, bring to a boil and then remove from heat. Transfer soup to a blender or, easier, use an immersion blender and blend the soup, adding in a half cup or more of heavy cream, tasting as you go. Season with fresh ground pepper and more salt if necessary, then chill thoroughly before serving. Garnish with the diced cooked potatoes, if reserved, or a chiffonade of sorrel leaves.