Yellowman (Northern Irish Honeycomb Toffee)

Instructions

1. Line a rimmed baking sheet with parchment and oil lightly. Measure the baking soda into a small bowl and set everything within reach.
2. Combine the sugar, golden syrup, butter, vinegar and water in a large, heavy saucepan (at least 3 quarts); the mixture will foam up later.
3. Cook over medium heat, stirring until the sugar and butter dissolve, then stop stirring and cook until a candy thermometer reads 300 F (150 C), the hard-crack stage, 15 to 20 minutes.
4. Remove from the heat and whisk in the baking soda quickly; it will foam and rise dramatically. Do not touch.
5. Pour at once onto the prepared sheet without spreading it; let the foam settle.
6. Cool completely, about 1 hour, until hard and glassy.
7. Break into chunks with a rolling pin or the back of a heavy spoon through a towel.