Ground cooked mung beans are used as an ingredient and a garnish in Vietnamese cooking. In both roles, they contribute a buttery richness, a highly desirable characteristic known as bùi. You must steam the yellow hulled and split beans, as they easily turn mushy and lose their nuanced flavor if boiled. A stainless-steel Chinese steamer is ideal because the tray is easy to manage and clean. If the tray holes are larger than 3/16 inch in diameter, line the tray with parchment paper, leaving a few holes uncovered for heat circulation. This is particularly important if you are steaming a small quantity of beans and don’t want to lose too many to the steamer bottom. It is not as crucial with a larger amount because the beans expand and stick together as they cook, forming a barrier of sorts. Dried mung beans expand to about three times their original volume during cooking, so if you need 1 cup cooked, start with 1/3 cup raw dried beans.
Because ground mung beans are a mainstay of the Viet kitchen, I typically buy a 14- or 16-ounce bag of beans, steam and grind the whole bag, and then freeze the ground beans in 1-cup portions for later use. They may be frozen for up to 3 months. Each portion will thaw at room temperature in about 2 hours.
