1. Preheat the oven to 120°C/100°C fan/gas mark ½. Grease two very large, shallow baking dishes with cooking spray. Add the popcorn, spreading it our evenly. Once the oven is preheated, place the popcorn in to warm through for 6-8 minutes.
2. Meanwhile, melt the butter in a saucepan over a medium heat. Stir in the sugar, golden syrup and salt.
3. Bring to the boil, stirring constantly. Once the mixture comes to the boil, leave to cook for four minutes without stirring.
4. Remove from the heat and stir in the bicarbonate of soda and vanilla extract. Pour the mixture in a thin stream over the popcorn, stirring to coat.
5. Transfer the toffee popcorn to the prepared baking dishes and bake for 45 minutes, stirring every 15 minutes.
6. Remove from the oven and allow to cool before breaking into pieces.

Per serving: 232kcals, 9.5g fat (5.7g saturated), 37.2g carbs (23.6g sugars), 1.7g protein, 1.7g fibre, 0.29g sodium