Toasted mochi are served in a sweet soup of an, made from azuki beans. The soup is made with the thin and pureed koshi-an, not with the thicker and chunkier tsubu-an. When tsubu-an is used, one speaks of zenzai instead of shiruko.
Like zenzai, delicious on cold winter days, but also an elegant dessert. Served in Japanese-style tearooms (kanmi-dokoro). Can also be bought ready-made in supermarkets.