Preheat your oven to 250°F (120°C). Line a large baking sheet with parchment paper or a silicone baking mat.
Place the popped popcorn in a large mixing bowl.
In a saucepan over medium heat, melt the butter.
Stir in the brown sugar, corn syrup (or honey), and salt. Cook, stirring constantly, until the mixture begins to boil.
Let it boil without stirring for about 4-5 minutes. The mixture will thicken slightly.
Remove the saucepan from heat and quickly stir in the baking soda and vanilla extract. Be careful as the mixture will bubble up.
Pour the caramel mixture over the popped popcorn and toss to coat the popcorn evenly.
Spread the coated popcorn onto the prepared baking sheet in an even layer.
Bake in the preheated oven for 45-60 minutes, stirring every 15 minutes to ensure even coating and prevent burning.
Remove the popcorn from the oven and let it cool completely on the baking sheet.
Break the cooled caramelized popcorn into clusters and serve.