Line a 20cm/8” square baking pan with baking paper. You’ll need to work quickly when the sugar is hot, so measure the baking soda and be sure to have a candy thermometer and wooden spoon handy.
In a large, heavy bottomed pan, stir the sugar and syrup together. Melt them over a low/medium heat, checking with a candy thermometer until it reaches 150C/300F (hard-crack stage).
Remove the hot sugar mixture from the heat, add the baking soda and quickly beat it in with a wooden spoon - be careful as the mixture will foam up and be very very hot!
Immediately pour the mixture into the prepared baking pan, then leave it to set at room temperature.
When it has cooled and set, cut or break it into shards.
Melt the chocolate in a microwave or in a bowl over a pan of gently simmering water, but don’t let the water touch the bottom of the bowl.
Dip the shards of honeycomb into the melted chocolate and sprinkle with a few flakes of sea salt. Allow the chocolate to set.
Be sure to gather all the ingredients and tools before you start. Once the toffee mixture is hot it's a very quick process!
When the sugar syrup begins to darken and reaches the hard crack stage, it's not long until it could burn. Work quickly (but carefully!) and take the pan off the heat.
Once the baking soda (bicarb of soda) is added to the oozy hot toffee mixture, it will fluff up and grow more than double in size. So choose a large or high sided pot.
It's important that your sugar is the right temperature or stage.
You can still make honeycomb without a thermometer - just scroll up for the method to determine hard crack stage without a thermometer.
Making honeycomb without a thermometer
Although a candy thermometer makes it easier to make homemade honeycomb, you can still make it without one.You'll just need to test the hot sugar syrup in cold water to reach the correct stage: hard crack stage.
Hard crack stage
With a food thermometer, you can easily determine if your hot sugar syrup has reached hard crack stage: test with the thermometer until it reaches 300F/150C.To tell if your sugar syrup is at hard crack stage without a thermometer, you'll need a bowl of very cold water.Once the hot sugar mixture begins to darken, take a small teaspoonful and drop it into the bowl of cold water. Leave it for a few moments the reach into the water and pick up the syrup. If it's soft and pliable, then it's at soft ball stage and is not ready. Try again until the sugar syrup instantly hardens in the water and 'cracks'.Please see this great short video about the stages of sugar syrup.