01 -
Preheat oven to 110°C. Line a large rimmed baking sheet with a silicone baking mat.
02 -
In a large heavy-bottomed pot, melt the butter over medium heat. Add the brown sugar, granulated sugar, corn syrup, and salt. Stir thoroughly to combine.
03 -
Continue cooking, stirring frequently, until the mixture begins to boil. Once boiling, stop stirring and allow to cook undisturbed for 5 minutes. Reduce heat to medium-low if mixture darkens too quickly.
04 -
Remove pot from heat. Immediately add ground cinnamon, baking soda, vanilla extract, and mini marshmallows. Stir until marshmallows are fully melted and mixture is smooth.
05 -
Arrange popped popcorn evenly on the prepared baking sheet. Pour hot cinnamon mixture over popcorn and carefully toss to coat thoroughly.
06 -
Transfer baking sheet to oven. Bake for 15 minutes, then stir to redistribute coating.
07 -
Continue baking an additional 15 minutes and stir again. Return to oven for 5–10 more minutes for optimal crunch, stirring once more before removing from oven.
08 -
Allow popcorn to cool completely on the baking sheet before breaking into clusters. Serve when fully cooled and crisp.