• Preheat the oven to 375°F. Grease a 14-inch round cake or pizza pan with unsalted butter. (See Kelly’s Notes.)
• In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, granulated sugar and brown sugar until light and fluffy, about 2 minutes.
• Add the eggs one a time, beating between each addition, then beat in the vanilla extract.
• Add the flour, baking soda, baking powder and salt and beat just until combined, then beat in the chocolate chips.
• Spread the cookie dough into the greased pan in an even layer. 
• Bake the cookie cake until it is pale golden and set in the center, 20 to 25 minutes. (For a softer cookie cake, underbake it.)
• Remove the cookie cake from the oven and let it cool completely. Once it has cooled, decorate it with frosting and sprinkles then slice and serve.

Kelly's Notes:

• To make a rectangular cookie sheet cake, you can also use this exact recipe but bake it in a half-sheet tray.
• The cookie will continue baking as it cools, so if you prefer a softer cookie cake it’s important to underbake it so that the center is just set when you remove it from the oven. 
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