Preheat oven to 250 degrees F.
Place popped popcorn in a very large bowl.
Prepare 2 sheet pans with nonstick spray and line with aluminum foil.
In a medium saucepan over medium heat, par-cook the bacon and render the bacon fat. Once the bacon has cooked, strain the bacon fat from the bacon pieces and reserve the fat. Transfer the cooked bacon pieces to paper towels and continue to drain the excess fat. Then add to popcorn.
In the saucepan already used, add the butter and bacon fat (add more bacon fat as needed). Heat until the butter has fully melted.
Add the brown sugar, corn syrup, and salt. Bring to a boil and stir constantly. Continue to boil without stirring for 4 minutes.
Remove from heat and stir in baking soda and vanilla.
Pour in a thin stream over popcorn, stirring to coat evenly.
Divide the mixture evenly between sheet pans and bake, stirring every 15 minutes for 1 hour. Remove from oven and let cool completely before breaking into pieces.
Store in an airtight container for up to one week.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.