Preheat oven to 350°F.
Line an 8x8 inch pan with parchment paper or non-stick baking spray and set aside.
Whisk together the dry ingredients in a large bowl: All-Purpose flour, cake flour, corn starch, baking soda, baking powder and salt. Set aside. 1 1/4 cup All-purpose flour, 3/4 cup cake flour, 1 tsp. cornstarch, 1/2 tsp. baking soda, 1/2 tsp. baking powder, 1/2 tsp. salt
Using a stand mixer fitted with the paddle attachment, cream the butter, white sugar and brown sugar together up to 4 minutes or until light and fluffy.
1/2 cup unsalted butter, cold, cut into cubes (8 Tbsp.), 1/4 cup granulated sugar, 1/2 cup brown sugar, packed (light or dark)
Add in the eggs, egg yolks, and vanilla extract.
1 large egg, 1 large egg yolk, 1 tsp. vanilla extract
Gradually add in the dry ingredients and then add in the Oreo cookies, mini chocolate chips and chopped cookies and creme bars.
15 Oreos, divided (10 get mixed into batter, 5 go on top), 1/2 cup mini chocolate chips*, 4 (1.55 oz.) HERSHEY’S Cookies ‘n’ Crème Bars , chopped*
Press dough into a prepared pan in an even layer.
Press more Oreo pieces on top and bake for ~20 minutes* or until a toothpick inserted into the center comes out mostly clean.
Let bars cool for ~15 minutes. Cut into bars and enjoy!