How to Make Giant Chocolate Chip Cookie Cake
For the cookie cake: Preheat the oven to 350 degrees F. Grease a 9-inch cake pan with nonstick cooking spray and line it with parchment. Set aside. Whisk the whole white flour and baking soda in a medium bowl; set aside.
Beat the butter, granulated sugar, salt, and brown sugar in a bowl of a stand mixer (or a large bowl) with a mixer on medium speed until fluffy, about 3 minutes. Beat in the egg and both types of vanilla until combined. Add the flour mixture and beat until just combined. Add the chocolate chips and stir with a wooden spoon or rubber spatula. Scrape the dough evenly into the pan and smooth the top.
Transfer to the oven and bake for 22-25 minutes or until the cake is lightly golden brown; this could take up to 30 minutes; depending on your oven, use a toothpick to test for doneness. Cover the cake loosely with aluminum foil after 15 minutes to avoid heavy browning around the edges.
Remove from the oven and let the cookie cool fully in the pan. Once cooled, use a knife or metal spatula to loosen the sides of the cookie cake from the pan and transfer it to a serving dish.
How to Make Chocolate Buttercream Frosting
Sift the powdered sugar and cocoa in a medium bowl to remove any lumps. In a small cup, combine 1 tablespoon heavy cream with ¼ teaspoon of espresso powder if using.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter with the salt on medium speed until it is very light and fluffy, about 3–4 minutes. Turn off the stand mixer, and add the powdered sugar mixture, heavy cream mixture, and vanilla extract.
Drape with a kitchen towel, mix on low speed until partially incorporated, then remove the towel. Increase to medium-high speed, and beat until smooth, about 2–3 more minutes.
Transfer the chocolate buttercream to a piping bag and decorate the Chocolate Chip Cookie Cake as desired or spread on the Chocolate Chip Cookie Cake to decorate, or transfer it to an airtight container and refrigerate until you’re ready to use it for up to 5 days. Enjoy!