When it gets cold around Japan, one of the most popular Japanese treats I love to eat is called, in Japanese, "shiru-ko" a hot azuki bean soup served two different ways, pulpy or smooth. Azuki is a legume that originated in the Himalayas over a 1000 years ago and has made its way all over asia until it reached Japan.
The smooth, or pureed version, has a mochi(sticky) rice cake in it. This version for me is the best because you don't have to spoon it out; you can just drink it from the bowl. For those who've never tried this, it's sweet. I love how it coats the mouth and palate. In between slurps I sip down some green tea and eat a fermented pickle in order to give the whole thing a nice balance between sweet, bitter, and sour flavor profiles.
Here in Japan, shiroku can be purchased from vending machines for as little as 100 yen. However, if you want the real authentic home taste then I can recommend a fantastic restaurant in Kamakura, Yokohama called in Japanese (Nango-shiru-koten). This is by far the oldest and most traditional restaurant for making the best sweet mochi soup. Most of the patrons are up in age, so you know it's a local favorite. The service is warm and excellent. Plenty of old decor and well maintained, clean, nostalgic.