Preheat oven to 350 degrees. Grease a 9 X 13" baking pan or line with parchment paper.
Blend butter, cream cheese, & sugar until creamy. Add the egg & vanilla and combine well.
Add in baking powder, baking soda, salt, & flour. Mix well until a thick dough forms.
Press dough into the bottom of prepared baking pan. Bake for 25 minutes. Cool completely before frosting
Blend butter & cream cheese until creamy. Add in the vanilla, mix well. Slowly mix in the powdered sugar until smooth & creamy.
Spread frosting over the cooled cookies. Put lots of sprinkles on top. Cut cookies into bars.