Preheat oven to 250.
Line a large baking sheet with aluminum foil; set aside.
Place the popped popcorn in a large bowl; set aside.
Melt butter in a small saucepan over medium-high heat.
Add brown sugar, corn syrup, and salt; stir until it starts to boil.
Let boil for 2 minutes without stirring.
Mix in baking soda and vanilla; mix until thoroughly combined.
Pour over popcorn, stirring to coat.
Add in chocolate chips and mix with a wooden spoon until chocolate is melted and thoroughly combined.
Spread popcorn over prepared baking sheet.
Bake for 30 minutes.
Remove, sprinkle with sea salt and let cool.
Garnish with chocolate chips and serve.