Dotori muk

Dotori-muk or acorn jelly is a Korean dish. It is a jelly made from acorn starch. Although "muk" means "jelly", when used without qualifiers, it usually refers to dotori-muk. The practice of making dotori-muk originated in mountainous areas of ancient Korea, when abundant oak trees produced enough acorns each autumn to become a viable source of food. Dotori-muk does not spoil easily, so it was used as a lunch food when traveling a long way. Despite being a rich source of starch and proteins, acorns contain large amounts of tannins and other polyphenols, which prevent the human body from digesting them properly. Harvested acorns must be properly leached of the tannins prior to consumption. Acorns are either collected directly from the ground or knocked off the tree branches. The acorns are opened and the nutmeat ground into a fine orange-brown paste. The paste is then stirred into vats of water and the acorns' fiber is separated from the starch through sieving and settling. The starch-water mixture is collected and allowed to sit so that the tannins in the starch diffuse into the water, which is changed several times. The overall soaking time depends on the amount of tannin in the paste.

Source: Wikipedia