Kashk is a dairy product that is essential to Persian cooking which can be dried or used in a paste form resembling yogurt. Candice Walker, who celebrates her Persian heritage on her food blog, Proportional Plate, describes Kashk as “a form of dried buttermilk.”

Kashk can help thicken soups and add a unique tangy flavor to all kinds of dishes, and if you can’t find it near you, a version of kashk can be made by mixing sour cream or crème fraîche with grated parmesan and a few “pulverized” anchovies. Cookbook author Naz Deravian recalls her family using it in aash-e reshteh, or aush reshteh, a green bean and noodle soup traditionally served on Noruz, the Persian New Year.

Kashk is also popularly used in kashke bademjan, an eggplant dip. Derivan writes, “To understand Iranian kashk is to appreciate the centuries-old art of preservation in Iranian cuisine,” explaining that, prior to modern refrigeration, shepherds in Iran turned to it as a means of preserving the gallons of milk that would otherwise spoil on their long journeys.