1. You will also need a sugar thermometer and 2 baking trays lined with parchment paper.
2. Microwave the popcorn according to the pack instructions, discard any un-popped kernals, then have it ready in a heatproof bowl.
3. Combine the butter, Lyle’s Black Treacle and Tate & Lyle Light Soft Brown Sugar in a large heavy-based pan and stir constantly over a low heat with a wooden spoon for about 10 minutes until the sugar has dissolved.
4. Bring to the boil without stirring, otherwise the sugar may crystallise, until the mixture reaches 149°-154°C, (300°-310°F) or the hard-crack stage. It will take about 10-12 minutes. If you don't have a thermometer you can check it is ready by dropping a teaspoon of the mixture into a bowl of cold water. It should harden instantly and, when removed, be brittle and easy to break. If not, carry on boiling it.
5. Carefully pour the treacle caramel over the popcorn, scatter over the Halloween sprinkles and, using two large spoons, very quickly stir everything together before the caramel cools and sets. Spoon into clusters onto the baking trays and leave to cool and harden.
Do keep children well away when you’re making the caramel as it can cause nasty burns.