EDITED: some people have reported that the cinder toffee has overflowed. Therefore, make sure you use a fairly deep dish (mine is 5cm in depth).
In a heavy bottomed pan, add the sugar and syrup and heat on a medium temperature until the sugar starts to melt.
Stir often, making sure the mixture doesn't stick, and continue to cook until it changes to a darker brown colour (this should take around 6-8 minutes but watch it carefully because it is very easy to burn).
Remove from the heat and then quickly add the baking soda, whisking it in to the hot mixture, then pour into the prepared tin. Move fast because the sugar mixture starts to harden almost immediately.
Set to one side until it has hardened completely (about 30 minutes).
In the meantime, melt the chocolate and then pour over the hardened honeycomb. Break, crush or cut up the gingerbread and sprinkle over. Allow the chocolate to set (it doesn't need to be in the fridge unless you are in a hurry).
When ready, break or cut into shards. The pictures in this post show very large pieces for photographic purposes which were broken into smaller pieces before eating.