Preheat the oven to 375F degrees.
In a small bowl, combine dry ingredients - flour, cornstarch, salt, baking soda, and baking powder. Mix with a fork or whisk to combine and set aside.
In a separate bowl, roughly crush 12 Oreos with your hands, or roughly chop with a knife, and set aside.
In the bowl of a stand mixer, place butter and both sugars. Mix, using a paddle attachment at medium to high speed for 3 minutes until light and fluffy. Scrape the sides of the bowl with a nonstick spatula.
Add in egg, egg yolk, and vanilla. Mix again until combined. Make sure to scrape the sides of the bowl again so that the dough is mixed evenly.
Add dry ingredients to stand mixer and mix dough until combined.
Add in crushed Oreos and chocolate chips and mix on low. Dough will be very thick!
Scoop dough into 4 oz balls.
On a parchment-lined standard baking sheet, place 4 dough balls at a time.
Bake for 8-11 minutes until sides are set. Cookies will be undercooked on the inside!
