MICROWAVE butter in large microwaveable bowl on HIGH 25 sec. or until melted. Stir in dry gelatin mix. Microwave 15 sec.; stir. Add marshmallows; toss to evenly coat. Microwave 1-1/2 min. or until marshmallows are completely melted and mixture is well blended, stirring after 45 sec. Add cereal; mix well. Press onto bottom of 13x9-inch pan sprayed with cooking spray; cool.
REMOVE cereal mixture from pan. Cut into snowflake shapes, using 3-inch cookie cutter. Insert blue paper straw into side of each.
MELT chocolate as directed on package; spoon into resealable plastic bag. Cut small piece off one bottom corner of bag; use to drizzle chocolate over cutouts as shown in photo. Top with sprinkles.