Make the cookie cake

1. Preheat oven to 350°F (180°C). Prepare a 9-inch cake pan with parchment paper in the bottom and baking spray on the sides. Set aside.
2. Combine the flour, baking soda and salt in a medium sized bowl and set aside.
3. Cream the butter and sugars together in a large mixer bowl on medium speed until light in color and fluffy, about 2-3 minutes. Scrape down the sides of the bowl a few times to be sure all is well incorporated. You should be able to see the change in color and texture happen and know it’s ready.
4. Add the egg and vanilla extract and mix until well combined.
5. Add the dry ingredients and mix just until well combined.
6. Chop 6 of the Oreo cookies and add them to the cookie dough. Place the remaining 6 Oreo cookies in a food processor and blend into crumbs. Add the crumbs to the cookie dough, along with the chocolate chips. Gently stir to combine the cookie dough with the chopped Oreo cookies, crumbs and chocolate chips. Do not over mix.
7. Press the cookie dough evenly into the cake pan. Press a few more chocolate chips into the top of the cookie cake, if desired.
8. Bake for 18-20 minutes, or until the edges just begin to turn golden.
9. Remove from oven and allow to cool completely in the cake pan, then transfer to a serving plate. It it’s fully cool, you should be able to flip it upside down onto a cooling rack, place another cooling rack on top (which is actually the bottom) and then flip it back over so that it’s right side up.

Make the frosting

1. To make the frosting, beat the butter in a large mixing bowl until smooth.
2. Slowly add 1 cup of powdered sugar. Mix until combined.
3. Mix in the vanilla extract, Oreo crumbs and one tablespoon of heavy cream.
4. Add the rest of the powdered sugar and mix until well combined and smooth.
5. Add additional cream, as needed, to get the right consistency buttercream.
6. Pipe swirls of frosting around the edge of the cookie cake (I used Ateco tip 844) and place half an Oreo between each swirl, then store in an airtight container until ready to serve. Because of the frosting, it should be refrigerated after about 24 hours, but should be served at room temperature. Best if eaten within 4-5 days.