Preheat the oven to 350°F. Line large baking sheets with parchment paper.
Cream the butter and sugar (3 min): In a large mixing bowl with an electric mixer, or in the bowl of a stand mixer fitted with the paddle attachment, cream together the cold butter, brown sugar, and sugar for 2-3 full minutes on high-speed, until light and fluffy.
1 cup cold unsalted butter, 1 cup light brown sugar, 1/2 cup granulated sugar
Add the eggs (2 min): With the mixer running on medium, add the eggs and egg yolk one at a time, mixing well after each one. Mix in the vanilla.
2 large eggs, 1 egg yolk, 1 teaspoon vanilla
Whisk dry ingredients (3 min): In a separate large bowl, whisk together the flour, cake flour, corn starch, baking soda, and salt.
1 1/2 cups all-purpose flour, 1 1/2 cups cake flour, 2 Tablespoons cornstarch, 1 teaspoon baking soda, 1/2 teaspoon salt
Combine the dough (2 min): Add the dry ingredients to the wet ingredients and mix on low until combined. Stir in the chocolate chips and crushed Oreos with a rubber spatula.
1 cup chopped semi-sweet chocolate bar, 2 cups crushed mint oreos
Scoop and bake (11 min): Using a heaping medium cookie scoop (about 3 Tbsp), drop the dough onto the prepared baking sheet and roll into a tall cone shape. Bake for 11-13 minutes (I baked mine closer to 13), until the edges are lightly golden brown.
Finish and cool (5 min): Right out of the oven use a large rimmed cup or bowl to swirl around the outside of the cookie to shape it into a circle. This also helps get the ripply edges. Press more chocolate chunks and chopped oreos into the top of the warm cookies. Allow to cool 5 minutes then transfer to a wire rack to cool completely.