Pop popcorn according to directions on bag. Use your hand to remove the popcorn from the bag into a large bowl and make sure not to let any stray kernels fall into the mix. No one wants to bite down on one of those! In a pot over medium heat, stir together brown sugar, corn syrup and butter. Allow mixture to come to a boil while stirring constantly. Boil for 2 minutes, while stirring, starting the timer when the first bubbles start to form around the outside.

Remove from heat and whisk in vanilla, sweetened condensed milk, canned pumpkin and pumpkin pie spice, until mixture is smooth. Pour over popcorn and toss gently with a wooden spoon to coat. The mixture likes to settle on the bottom of the bowl, so be sure to stir it up from there. Keep in an airtight container to preserve freshness.