Preheat your oven to 250°F (120°C). Line a baking sheet with parchment paper.
Pop the popcorn and place it in a large bowl, making sure to remove any unpopped kernels.
In a medium saucepan, melt the butter over medium heat. Stir in the sugar, corn syrup, and salt. Bring the mixture to a boil, stirring constantly.
Once it reaches a boil, stop stirring and let it boil for 4-5 minutes. Remove from heat and stir in the vanilla extract, baking soda, and a few drops of yellow food colouring if you’re using it.
Pour the mixture over the popcorn and stir to coat evenly.
Spread the popcorn onto the prepared baking sheet.
Bake in the preheated oven for 45-60 minutes, stirring every 15 minutes, until the popcorn is crisp and golden.
Let it cool completely before enjoying it.