The offerings rice cake

Japanese make the offerings rice cake(KagamiMochi) in New Year. Its shape is round like a mirror(kagami). After New Year, they breake hit the offerings rice cake with a mallet. And put breaked small rice cakes, make Zoni. This seasonal event is called "Kagami-biraki". Because cutting is taboo, doesn’t use a kitchen knife.

See also
*List of Japanese culture