Anko  (あんこ or 餡こ) is a sweet red bean paste made from Adzuki beans that have been cooked until tender and then sweetened with sugar as it is cooked down into a thick paste. It can be prepared with whole beans remaining for tsubuan (粒あん), or it can be mashed and passed through a sieve to make a smooth paste known as koshian (こしあん).