Yōkan : Its history and the different varieties
Yōkan is originally a Chinese dish – a soup featuring mutton – which was introduced to Japan around the 13th-14th centuries. The prohibition for Buddhist monks against eating meat meant other ingredients were added to the soup, such as steamed dumplings fashioned from azuki beans, rice and flour.
The steamed dumplings were served without soup as a sweet with the spread of tea ceremony in around the15th and 16th centuries. Agar, which can set liquids in the same manner as gelatine, began to be used from about the 17th century. Sugar and agar were simmered and added to pureed azuki beans, and set in wooden moulds into rectangles or bars. This is the most popular variety of yōkan today.
Sugar and azuki beans were costly, however, which meant yōkan was out of the reach of most people. A sweet shop in Tokyo came up with a variety of yōkan (imoyōkan) using inexpensive sweet potatoes around 1900.
There are also varieties of yōkan made with local produce, e.g. chestnuts, persimmons, apples.