Crunchie is a brand of chocolate bar with a honeycomb toffee centre. It is made by Cadbury but was originally launched in the UK by J. S. Fry & Sons in 1929.
Crunchie
A Crunchie split in half
A close-up of the bar's honeycomb centre
Honeycomb toffee, honeycomb candy, sponge toffee, cinder toffee, seafoam, or hokey pokey is a sugary toffee with a light, rigid, sponge-like texture. Its main ingredients are typically brown sugar and baking soda, sometimes with an acid such as vinegar. The baking soda and acid react to form carbon dioxide which is trapped in the highly viscous mixture. When acid is not used, thermal decomposition of the baking soda releases carbon dioxide. The sponge-like structure is formed while the sugar is liquid, then the toffee sets hard. The candy goes by a variety of names and regional variants.
Honeycomb toffee
A street seller in Asakusa Tokyo offering hand-made karumeyaki