Combine popcorn and chopped Butterfinger in large bowl.
Melt butter in medium saucepan over low heat. Stir in marshmallows. Heat, stirring constantly, until marshmallows are melted and mixture is smooth.
Pour over popcorn mixture; quickly toss to coat well. Coat ice cream or cookie scoop with nonstick cooking spray. Scoop popcorn mixture into 25 (1 1/2-inch) balls. Place on wax paper to cool. Wrap in decorative bags or store in airtight container.