Bake the cake as directed and let cool completely before crumbling and mixing with the frosting and ½ cup of the sprinkles until fully combined.
Roll into 1 tablespoon sized balls and freeze for 60 minutes.
Melt the white chocolate in the microwave in a microwave safe bowl in 30 second increments until smooth then dip each ball on top of a fork into the white chocolate, tap to remove the excess then place onto a parchment paper lined baking sheet.
Using a small ziplock baggie with some extra melted white chocolate in it, snip off a tiny edge of the bag and zig zag over each truffle then sprinkle more rainbow jimmies on top and allow to harden completely.
