Sponge toffee is a sugary confection with a light, rigid, foam-like texture.
The main ingredients are typically brown sugar, corn syrup (or molasses) 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 lattice structure is formed while the sugar is liquid, then the candy sets hard.
It is generally home-made, and a popular recipe for children, but is also made commercially and sold in small blocks, or covered in chocolate (most popularly the Crunchie or Violet Crumble bar).
