Preheat your oven to 350°F. Line two baking sheet swith parchment paper and set aside.

In a large bowl using a stand or hand mixer with the paddle attachment, cream the butter, brown sugar, and granulated sugar together on medium speed until light and fluffy, about 2-3 minutes. With a rubber spatula, scrape down the sides and bottom of the bowl.

Add the egg and mix on medium speed for 20 seconds, scrape down the sides and bottom of the bowl. Add the egg yolk and mix for 20 more seconds until combined. Add the vanilla and mix on low just until combined.

Add the flour, baking soda, baking powder, cornstarch, rainbow sprinkles, golden Oreo pieces, and salt to the wet ingredients and mix on low speed until combined and no more flour streaks remain

Use a four-tablespoon cookie scoop to portion the dough onto the prepared baking sheet, spacing cookies at least two inches apart. For smaller cookies, use a three-tablespoon scoop.*

*if you don’t have a 4 tablespoon scoop use a 3 tablespoon size cookie scoop and bake for 10 minutes instead of 13.

Bake at 350°F for thirteen minutes for large cookies. The edges should be just set — the centers will look slightly underdone, which is perfect!

Immediately after removing from the oven, press the reserved golden Oreo pieces gently onto the tops of each cookie. Allow the cookies to cool on the baking sheet for at least ten minutes before transferring as they will firm up as they cool.