Put the sugar and golden syrup in a saucepan and cook over low heat. Cook until it takes on a darker color and starts to bubble. Stir to ensure it doesn't burn.
Once bubbling, cook for another 2 min., then add the baking soda and stir vigorously.
While the mixture is still frothy, pour onto a sheet of parchment paper and leave to cool.
Once it has set and hardened, wrap up the toffee in the parchment paper and break it into small pieces by hitting with a rolling pin.
Whisk the double cream until thick but still pourable, then add the condensed milk and whisk until the mixture holds its form.
Add the pieces of honeycomb toffee and fold in with a rubber spatula. Pour the mixture into a container and leave to freeze for at least 4 hrs.