Preheat your oven to 325 degrees F and line a baking sheet with parchment paper or a silicone baking mat.
Pour your popped popcorn into a large mixing bowl, making sure to remove any unpopped kernels, and set aside.
In a saucepan over medium heat, bring the butter, brown sugar, and corn syrup to a rolling boil, then continue to boil for 1 minute.
Remove from the heat and stir in 1 tbsp cinnamon, baking soda, and vanilla extract. Pour the mixture over the bowl of popcorn, then mix to coat evenly.
Transfer the popcorn to your prepared baking sheet, spread it into an even layer, and bake for 10-12 minutes, tossing halfway through. Let cool completely.
In a microwave safe bowl, combine white chocolate chips with vegetable oil. Microwave in 30 second intervals, stirring in-between, until melted and smooth. Once melted, stir in the remaining cinnamon.
Evenly drizzle the melted chocolate over the cooled popcorn, then let the chocolate set completely before breaking into pieces and enjoying!