Line a large baking sheet with parchment paper or a silicone mat. Set aside.
Pop popcorn kernels using air popper into a large bowl.
In a small saucepan melt butter, brown sugar, corn syrup and 1 tsp salt together over medium heat. Bring to boil. Boil for 4 minutes without stirring.
Pour caramel mixture over popcorn and stir to coat evenly.
Pour popcorn into lined pan, sprinkle remaining salt on top (1/2 tsp - 1 tsp depending on your personal taste preference) and place in oven. Bake for 30 minutes, stirring every 10 minutes.
Allow popcorn to cool on a parchment lined counter.
