Copycat CrunchieTM-Style Chocolate Coated Sponge Toffee

Instructions

1. Line an 8-inch (20 cm) square pan with parchment paper, letting it hang over all four sides. Place the pan on a baking sheet to catch any overflow of sponge toffee.
2. Place a sieve on a small plate and pour in the baking soda. Keep this close by as you work, ready to use, along with a whisk and a silicone spatula.
3. In a 12-cup (3 litre) pot, off the heat, combine the corn syrup and sugar. Mix until the syrup has soaked up the sugar. Bring to a boil over medium heat, without stirring, until a candy thermometer reads 300°F (150°C). The mixture will be only slightly golden.
4. Immediately remove the pot from the heat. Sift the baking soda over the boiling syrup. Working quickly, whisk the mixture 4 to 5 times, then immediately pour into the prepared pan using the silicone spatula. Watch out for splattering. The mixture will bubble up significantly.
5. Let cool at room temperature for 2 hours. The sponge toffee will deflate slightly as it cools.
6. Unmould the sponge toffee onto a work surface. Using a kitchen mallet, break the toffee into pieces.