In heavy saucepan on medium to medium-high heat melt butter then add brown sugar, corn syrup and salt.

Bring mixture to a boil stirring constantly.

Once mixture boils stop stirring and boil for 5 minutes (Do not stir). Remove from heat and carefully stir in vanilla and baking soda. Pour mixture over popped corn. Gently stir to coat popcorn.

Place popcorn into a large roaster or rimmed baking sheet and bake at 225° F for 1 hour, stirring every 15 minutes. Cool and enjoy!