Place popped popcorn in a large bowl, removing any unpopped kernels. Set aside. Place ice cream in a large microwave-safe bowl. Microwave on high 30 seconds or until ice cream is melted. Add marshmallows; stirring to coat. Microwave on high 1 minute or until marshmallows are softened (almost melted); stir until smooth. Stir in non-fat dry milk powder. Pour this mixture over popped popcorn, stir until well coated. Stir in 1/4 cup malted milk powder. Spray hands with non-stick cooking spray and form popcorn mixture into 1-1/2 inch diameter balls. Sprinkle lightly with confetti sprinkles and roll in additional malted milk powder, if desired. Set on waxed or parchment paper. Let stand several hours.