An

An is a sweet paste usually made from sugar and boiled and mashed adzuki (red beans). The food item came from China as a steamed bun with a meat filling. At that time, though, the Japanese were strict Buddhists, did not eat meat, and so filled the bun with bean paste instead.

The term an now refers to almost any kind of paste. Shiro-an is a white bean paste made from white-colored beans; black sesame seeds result in a dark grey form; green peaks make an olive-green jam, and sweet potatoes make a greenish-yellowish paste.

Texture also varies. If you mash the boil ingredients with sugar you end up with a granular texture material called tsubu-an. If you strain the paste to get a smooth texture you end up with koshi-an.

Both of those forms are generally desert dishes. It can also be used a stuffing or steam buns (manjuu), or balls of steamed and pounded sticky rice (mochi). It can be used as a topping on dango (rice dumplings), or as botamochi (rice balls). Shiruko is a soup made of adzuki bean paste and soft mochi. It can also be added to boiled and processed seaweed. The material is beaten and allowed to gel, yielding a firm and sweet material called yookan.

Adzuki beans are rich in vitamin B1 and potassium..