Line a cookie sheet with parchment paper and set aside
Pop and prepare about 8 cups of popcorn. Set aside in a large mixing bowl.
In a medium saucepan, melt the butter over medium heat. Add the marshmallows and stir until completely melted and smooth.
Remove from heat. Stir in the brown sugar, vanilla extract, pumpkin spice, cinnamon (if using), and a pinch of salt until well combined.
Pour the marshmallow mixture over the popcorn. Use a spatula to gently fold until the popcorn is evenly coated.
Spread the popcorn on a baking sheet lined with parchment paper. Let it cool for about 10–15 minutes before serving to let the marshmallow coating set slightly.
Notes
Optional Add-Ins:
Drizzle melted white or dark chocolate over the top.
Toss in some pumpkin seeds, pecans, or crushed graham crackers for extra texture.