Preheat oven to 250°F. Pop the popcorn kernels in an air-pop popcorn machine until fully popped.

Divide the popcorn evenly between 2 large baking sheets lined with silicone baking mats or parchment paper, leaving behind unpopped kernels.

In a medium saucepan, combine the butter, light brown sugar, light corn syrup, and kosher salt. Melt slowly over medium heat, stirring constantly until smooth.

When mixture comes to a full boil, continue to boil for 5 minutes, stirring constantly.

Remove from heat and add the baking soda. Mix in baking soda carefully as the mixture will expand.

Divide the caramel between the 2 large baking sheets and mix well to coat the popped kernels evenly.

Bake for 1 hour, stirring every 15 minutes until golden brown. Cool completely and enjoy!