Firstly, line an 8x10inch baking tin (with high sides) with baking paper, and grease lightly with butter. Then set aside on a cooling rack.
Combine the sugar and golden syrup in a large pan and place over a medium-high heat. Cook, stirring every now and then, until the sugar has melted and its turned a golden-amber colour. Then take off the heat and quickly sprinkle the bicarbonate of soda in, and stir quickly to combine. It will foam up at this point.
Quickly pour into the prepared tin while still foaming and leave to set.
Break up the honeycomb into pieces. Then melt both the milk chocolate and dark chocolate in separate bowls (either using a bain-marie or in the microwave). Dip the honeycomb pieces into the chocolates, using a fork to help turn and tap any excess chocolate off the pieces. Then place onto baking paper to set. Then place in air-tight containers or bags.
Will keep up to 1 month in air-tight containers or bags.