Wikipedia
Oksusu cha (literally "corn tea") is a traditional Korean infusion made from boiled roasted corn kernels.
The variety of corn most often used is called Gang-naeng-i (강냉이), which is usually grown in the area of Gangneung, a city in the Gangwon province on South Korea's eastern coast, thus making this drink particularly popular in that region. To prepare oksusu cha, corn kernels are thoroughly dried and then roasted until they turn golden brown or brown. Then the roasted corn is brewed with boiling water until the drink's color turns a pale yellow. The tea is then strained and the boiled corn discarded. Roasted corn is available at markets, and in prepared tea bags as well. Although the drink is naturally sweet, sugar may be added to oksusu cha if a sweeter flavor is desired. Oksusu cha is often combined with bori cha (roasted barley tea), as the corn's sweetness offsets the slightly bitter flavor of the barley.
Oksusu cha is traditionally thought to be good for those with high blood pressure, diabetes, and kidney disease.