1. Preheat oven to 300 degrees, and line a jelly roll pan with parchment paper. Spread popcorn out onto the pan, set aside.

2. Place butter and corn syrup into a small pan, heat on low until butter is melted. Add sugar and Jello to the pan, and stir until the gelatin has dissolved. Bring to a boil over medium heat, reduce heat to low and simmer for 5 minutes.

3. Pour candy liquid over the popcorn, tossing well to coat. Mix in the marshmallows. Spread it out with greased hands, or using two forks.

4. Bake for 10 minutes, stirring half way through. Remove from the oven and immediately begin to break apart using your fingers or two forks. Allow to cool completely, and store in an air tight container.