Line a 22cm (9 inches) square baking tin with greaseproof non-stick baking paper.
Place the caster sugar and honey or golden syrup into a saucepan with high sides and heat over low heat. The sugar will start to dissolve.
Once the sugar has dissolved turn the heat up and whisk until the mixture reaches a temperature of 140c/300f.
Quickly whisk the bicarb into the mixture to combine and pour into the pan and leave to cool. Once the mixture is in the pan don’t move it or touch it. This will knock the air out of it.
Melt the chocolate in the microwave and use a fork to dip the cider toffee chunks. Lay them on a cooling rack to set the chocolate.
Break into chunks and store in an airtight container for about 3 days.
Notes
Use a thermometer to the best accuracy.
Moisture is the enemy of cinder toffee. Be sure to store it in a dry airtight container for up to 3 days.
Be sure that the cinder toffee is completely set before breaking apart.