Prepare a 20cm/8" square tin by greasing with butter, cake release spray or Lining Paste. (For other tin sizes see notes). Add the sugar and Golden Syrup to a deep pan (not a non-stick one), and mix together. On a low-medium heat, stir the mixture until the sugar has dissolved. I find the best way to get the golden syrup off the tablespoon is to coat it in oil, then the syrup falls off the spoon easily. You need to not use a non-stick pan because the high temperatures ruin the non-stick coating and can release toxins into the food.
Once the sugar and syrup have melted turn the heat up to medium. Cook until the mixture turns amber & is at the hard crack stage. Some sugar/candy thermometers have this on it, but if not, you are looking for a temperature that reads 146°c or 295°f. And for me it takes about 10 mins. You need to be keeping a close eye on this as any higher the mixture will disintegrate very easily and will lack a nice crunch.
Now this is where you have to be really quick and careful. Once the mixture reaches the correct temperature immediately remove the pan from the heat and add the Bicarbonate of Soda (Baking Soda) and beat vigorously until no longer visible and the mixture is foaming.
Scrape the mixture into the greased tin right away & be careful as the mixture is very hot.
Clean the pan straight away – pour in boiling water to help dissolve the sugar and make it easier to clean.
Leave the honeycomb to bubble away, for about 1½ hours, at which point it will become hard. Then attack it with either a toffee hammer or end of a rolling pin! Be careful as it does splinter a bit so do it on a clear work surface.
I liked to do some with chocolate on so just melt some broken chocolate in the microwave in 30 second bursts, mixing in-between each burst. Alternatively, melt in a bowl over a pan of barely simmering water. Just dip the end of the honeycomb into the melted chocolate and place on some baking/parchment paper till set.