Preheat oven to 350 degrees.
Line a 9×9” pan with nonstick foil.
Beat cake mix, butter and egg.
Add 1/3c. sprinkles.
Press 2/3 into pan.
Sprinkle on the white chips and other 1/3c. sprinkles.
Pour on the condensed milk.
Flatten rest of dough and patch on top of the milk to create a top layer.
Bake about 30 mins.
Cool, chill and cut.