Preheat oven to 250°F. Grease 2 baking sheets with coconut oil or spray. 

Divide popped corn between baking sheets and set aside.

In a medium saucepan, simmer brown sugar, corn syrup, coconut oil, and salt until a thermometer registers 250°F. 

Stir in vanilla and baking soda. The mixture will foam, so be careful!

Pour caramel sauce over popcorn, dividing it between 2 trays, and stir to coat. Stir in peanuts. 

Bake at 250°F for 1 hour, stirring occasionally. The caramel sauce will harden as it bakes. Be sure to break up any large clumps or corn that stick together. 

Cool before storing, covered, at room temperature. The caramel corn will stay crunchy for about 2 days if kept out of humidity.