Preheat oven to 350F
Line 10 inch cake pan with parchment and grease.
Beat butter and sugars.
Add eggs and yolk
Add vanilla extract.
On low, add flour, cornstarch, baking powder, and salt.
Fold in chocolate chips and sprinkles.
Spread batter into pan.
Bake 24-26 mins.
When cool, pipe on frosting and add more sprinkles!