Higashi is a general term for “dry” sweets. Those of us practicing tea, know them mostly as the pressed sugar candies called uchimono we have with usucha.
The recipes for higashi are closely guarded secrets to the confection shops that make them. They are mostly made from a special Japanese sugar called wasanbon. I have heard of it being mixed with small amounts of rice flour or egg white, and of course food coloring.
When the mixture is the correct texture and consistency, it is hand-pressed into molds carved out of wood. The sweets take on the shape and design of the carved molds— usually very beautiful designs of flowers or other natural objects.
Since the higashi contain very little moisture, they have quite a long shelf-life. I like to keep mine in the refrigerator if I’m not going to use them right away (say, within a few weeks).