First, pop 100 grams of popcorn kernels in a large pot over medium heat with a little oil. Once popped, transfer the popcorn to a large bowl, ensuring there are no unpopped kernels.
In a separate pan, melt 200 grams of unsalted butter over medium heat. Add 400 grams of brown sugar, 1 teaspoon of salt, and ½ teaspoon of baking soda. Stir until the sugar is completely dissolved.
Bring the mixture to a boil and let it simmer for about 4-5 minutes without stirring. Remove from heat and immediately stir in 1 teaspoon of vanilla extract.
Pour the hot caramel over the popcorn. Use a spatula to gently toss and coat the popcorn with the caramel. Be careful as the caramel will be extremely hot.
Preheat your oven to 120 degrees Celsius. Spread the caramel-coated popcorn on a baking sheet lined with parchment paper.
Bake for 45 minutes, stirring every 15 minutes to ensure even coating.
Remove from the oven and let it cool completely before breaking into pieces.