Beat cake mix, butter, and egg together in a large bowl on medium speed until evenly blended.
With clean hands, knead mixture until smooth and dough-like.
Stir in sprinkles.
Spray a small pan with nonstick, turn your batter out onto the pan, and smooth down with your hands to form a single sheet. We used a 9x9 non-stick cake pan.
Sprinkle chocolate chips on top, followed by more sprinkles.
Bake at 350 for about 22 to 26 minutes (edges should turn golden brown)
Remove from oven, cool, and cut.
Optional: Spread your favorite icing on top and serve!
Video
Notes
If you use a glass baking dish, you may need to bake for between 28 to 30 minutes. We don't recommend making this recipe in a glass baking dish as the edges cook faster and the center takes much longer to bake through.