Giant Chocolate Chip Cookie Cake:

1. Preheat your oven to 350°F. Line the bottom of a 9 inch springform pan with parchment paper and set aside.
2. In a medium bowl, whisk together flour, cornstarch, baking soda, and salt to combine. Set aside.

   - 2 cups (260g) all-purpose flour, 2 tablespoons cornstarch, 1/2 teaspoon baking soda, 1/2 teaspoon salt

3. In a large bowl, combine butter, brown sugar, and granulated sugar. Using an electric mixer fitted with the paddle attachment, cream together on medium high speed until light and fluffy.

   - 3/4 cup (175g) unsalted butter, 3/4 cup (150g) brown sugar, 1/2 cup (100g) granulated sugar

4. Whisk in the eggs one at a time followed by vanilla.

   - 2 large eggs, 2 teaspoons pure vanilla extract

5. Add the dry ingredients and mix together until almost combined. Stop right before the flour is fully incorporated then drop in the chocolate chips.

   - 3/4 cup (130g) semi-sweet chocolate chips

6. Fold in the chocolate chips until combined and you have a sticky, streak free cookie dough.
7. Drop the cookie dough into your prepared springform pan and spread into an even layer. Sprinkle some more chocolate chips on top if desired.
8. Bake the cookie in the center of your preheated 350°F oven for 25 to 30 minutes or until evenly puffed and the edges are golden brown. The center will be a bit pale in color. 
9. Cool the cookie for about 20 minutes in the pan then run a knife around the edges to release any stuck on bits. Unlatch the sides of the springform pan and lift them off (but leave the cookie on the bottom disk of the pan).
10. Finish cooling the cookie COMPLETELY to room temperature before frosting. The center will sink and darken slightly as it cools.

Buttercream Frosting:

1. In a large bowl, combine frosting ingredients. Mix together until smooth and fluffy. If the frosting is too thick, mix in some more milk. If it's too thin, mix in some more powdered sugar.

   - 1/4 cup (50g) unsalted butter, 1 1/2 cups (180g) powdered sugar, pinch of salt, 1 teaspoon pure vanilla extract, 1-2 teaspoons milk or heavy cream

2. Frost the cooled cookie cake and top with some sprinkles if using. For a gooier cookie, serve the same day. For a fudgier and chewier cookie, cover and let it sit for a few hours or overnight to fully set in the center.