Prepare your tin/dish by lining with lightly oiled baking parchment.
Heat the sugar, golden syrup, water and vinegar until it starts to turn amber and reaches 150C/the hard crack stage (explanation above).
Add the bicarb and stir thoroughly, then pour into your lined tin. Leave to cool to room temperature.
If you want it to be cut into ordered shapes, cut with an oiled knife when its nearly it room temperature. I like it to look a little rough and tumble so cut it when its cool.
Store in an air tight container or gift to friends in small transparent bags or jars. It is delicious covered in chocolate or with chocolate mousse.
Recipe originally from http://eatlikeagirl.com/2010/12/19/a-recipe-for-yellowman-aka-honeycomb-cinder-toffee/