Make the caramel sauce by melting the butter, brown sugar, and corn syrup together.
Bring the mixture to a boil and let it boil for 5 minutes, stirring constantly.
Remove from heat and stir in the baking soda.
Pour the caramel sauce over the popcorn and stir to coat evenly.
Spread the caramel popcorn onto a baking sheet and bake at 250°F for 1 hour, stirring every 15 minutes.
