Preheat oven to 350°F. Line the bottom of a 9-inch springform pan with parchment paper or grease, plus lightly grease the sides. You may also use a greased 9-inch pie plate.
In a medium mixing bowl, use an electric mixer to cream the butter and sugars for about 3 minutes until light and fluffy. Add the egg and vanilla, and mix until combined.
In a separate bowl, combine the flour, cornstarch, baking soda, and salt. Add the flour mixture gradually to the butter mixture. Beat on low until combined. Stir in the chocolate chips. Spread cookie dough into the prepared pie plate.
Bake for about 20-25 minutes or until golden brown on the edges. The middle should still be light. Cool in pan on wire rack. Once cooled, decorate with your favorite frosting recipe.
Once cooled, decorate with your favorite frosting recipe. I used a Wilton 2C piping tip.