a zweiback cake?
you could hurt someone with a zweiback cake. it would be like a giant hockey puck.
here in the u.s., zweiback are very hard little biscotti-like cookies. like urm said, they used to be given to babies to help with teething. unfortunately, many doctors warn against giving them to teething children nowadays as a large piece may break off and present a choking hazard to the baby.