In a large bowl or the bowl of a stand mixer, cream together butter and sugar. Beat in egg yolks and vanilla. Add flour, baking powder, and salt, and mix until just combined.

Roll the dough into balls slightly bigger than a tablespoon. The dough will be thick but should roll into a ball shape with the heat of your hands.

Roll each ball of dough in sprinkles and place on prepared baking sheet. Bake 8-10 minutes. Cookies will look under baked.

Let cool 5 minutes after removing from the oven, then place a kiss in the center of each cookie.