Cook popcorn on the stovetop, Instant Pot, or in a popcorn maker.
Pour into a bowl and set aside.
Preheat oven to 300 degrees and spray a cookie sheet with cooking spray.
In a saucepan, combine the brown sugar, butter, and salt.
Cook until butter is melted. Continue cooking for 3 minutes without stirring.
Add baking soda and vanilla extract, stir to combine.
Pour over popped corn and stir well.
Spread evenly onto the prepared cookie sheet.
Bake for 15 minutes at 300 degrees.
Cool completely.
Store in an airtight container.