Preheat the oven to 180oC and line a baking tray with baking parchment.
To make the honeycomb, stir together the caster sugar and golden syrup in a saucepan. Cook over a medium/high heat until the mixture is a deep amber colour and then remove from the heat and rapidly whisk in the bicarbonate of soda. Pour the bubbling sugar onto the baking tray and leave to harden.
Meanwhile, make the shortbread. Place the flour, caster sugar and butter into a food processor and pulse until the mixture begins to clump together. Pour out onto a large sheet of clingfilm.
Place the hard honeycomb into the food processor and pulse until chopped into small pieces. Add half of the crushed honeycomb into the dough, knead briefly and then roll into a log and freeze for at least 15 minutes.
Slice the dough into 14 rounds. Bake for 10-12 minutes and then leave to cool completely.
Dip the edges of the shortbread into the melted chocolate and then into the remaining crushed honeycomb before allowing the set.
