Misu

Misu is a beverage made from the traditional Korean grain powder misu-garu (미숫가루; misutgaru; lit. misu powder), which is a combination of 7–10 different grains. It is usually served on hot summer days to quench thirst or as an instant nutritious drink for breakfast or as a healthy snack. In a Joseon Dynasty (1392–1897) recipe book, misu was mentioned as stir-fried barley (gu). Gu was a delicacy of that time and easy to serve as one went to travel.

Source: Wikipedia