Step 1

Preheat oven to 350°F. Line a 9x9” pan with foil and spray liberally with cooking spray.

Step 2

Add cake mix, butter, and egg to the bowl of an electric mixer fitted with a paddle attachment. (You can also use a hand mixer.) Mix until a thick dough forms. This will take a long time, especially if you're using a hand mixer. Just keep mixing! Add sprinkles and stir until incorporated.

Step 3

Press about 1/2-2/3 of the dough into the bottom of the prepared pan.Pour sweetened condensed milk over the top of the dough, leaving a thin border around the edges. Sprinkle with white chocolate chips. Separate remaining dough into small balls and evenly space over the top of the bars. Press down to flatten. Try to seal the edges as much as possible.

Step 4

Bake bars for about 25-30 minutes, or until they just begin to brown. Cool completely before slicing, otherwise the mixture will be too gooey to cut.