Method

1. Grease a 20cm/8in square baking tin with groundnut oil, then line with baking paper and grease again.

2. Place the butter in a deep, heavy-bottomed pan with the sugar, condensed milk and golden syrup. Heat over the lowest heat, stirring constantly with a wooden spoon to dissolve the sugar.

3. Put a sugar thermometer in the pan and increase the heat slightly to bring the mixture to a gentle boil. Cook, stirring constantly until the temperature reaches 118C/245F. (CAUTION: boiling sugar is extremely hot. Handle very carefully. Use a deep pan to avoid bubbling over.)

4. Take the pan off the heat and use a wooden spoon to stir in a generous pinch of rock salt, the liquorice powder and black food colouring. Beat the mixture well until the black paste colours it completely.

5. Pour the caramel into the prepared tin and scatter with rock salt. Leave to cool for one hour, then place in the fridge. Leave overnight before cutting into squares. Wrap each square in a piece of parchment paper.

6. Enjoy with a coffee or give to your friends as a gift.