Mix popcorn, corn flakes, and malted milk balls in a large bowl.
Place white chocolate in a microwave-safe bowl. Microwave until white chocolate is completely melted, stirring after each 1-minute interval. Stir malted milk powder and shortening through the melted white chocolate until smooth.
Pour white chocolate mixture over popcorn mixture; toss to evenly coat. Spread popcorn mixture onto the prepared baking sheet. Refrigerate until set, about 30 minutes. Break apart and store in an airtight container.
