Step 1

Preheat the oven to 350°F (177°C). Spray a 9-inch springform pan with nonstick cooking spray and set aside.

Step 2

In a large mixing bowl, whisk together the flour, baking soda, and salt. Set aside.

Step 3

In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a handheld mixer, cream together the butter, brown sugar, and granulated sugar for 1 to 2 minutes or until well combined.

Step 4

Add the egg, egg yolk, and vanilla extract and mix until fully combined, making sure to stop and scrape down the sides of the bowl as needed

Step 5

Mix in the dry ingredients until just combined. Then, mix in the chocolate chips on low-speed until fully incorporated into the cookie dough.

Step 6

Scoop the cookie dough into the prepared springform pan and spread it out into one even layer.

Step 7

Bake for 22 to 28 minutes or until the top of the cookie cake is set and lightly browned. Cover loosely with foil if needed to prevent excess browning on top of the cookie cake.

Step 8

Remove from the oven and allow to cool completely before removing from the pan.

Step 9

In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a handheld mixer, beat the butter for 1 to 2 minutes or until smooth. Add the powdered sugar ½ cup (60 g) at a time, mixing in each addition until well combined.

Step 10

Add the cocoa powder and mix until fully combined, then add the heavy whipping cream and vanilla extract and continue mixing until well combined, stopping to scrape down the sides of the bowl as needed.

Step 11

Release the cooled cookie cake from the springform pan. Pipe the frosting around the edges of the cookie cake.