In a large bowl, mix together popcorn and Sun-Maid Raisins. Set aside.
Melt butter in a medium pot over low heat. When melted, stir in mini marshmallows. Once mini marshmallows have fully melted, stir in cake mix.
Working quickly, pour mixture over popcorn and raisins and toss. Mix in sprinkles, then spread popcorn on a parchment-lined sheet tray.
Place white chocolate chips in a microwave-safe bowl. Microwave until melted, using 30-second increments and stirring in between.
Drizzle popcorn with melted white chocolate and let cool before serving.