In large bowl, mix popcorn and cereal; set aside. In 1-quart saucepan, melt marshmallows and 3 tablespoons of the butter over low heat, stirring occasionally, until marshmallows are melted and mixture is smooth. Pour over popcorn mixture; stir until well blended. Spray hands with cooking spray. Shape popcorn mixture into 20 (2-inch) balls; place on ungreased cookie sheet.
In small microwavable bowl, microwave remaining butter and the chocolate chips uncovered on High about 30 seconds, stirring every 15 seconds, until melted and smooth; cool 2 minutes. In 1-pint resealable food-storage plastic bag, carefully spoon melted chocolate; seal bag. Cut small opening diagonally across bottom corner of bag; pipe chocolate over tops and sides of popcorn balls. Let stand 5 minutes or until chocolate sets. Wrap individually in plastic wrap, or in food-storage plastic bags; tie with ribbon or raffia.