Preheat oven to 350°F (177°C). Lightly grease your 12-inch or larger pizza pan. (No smaller than 12 inches.)

Whisk the flour, cornstarch, baking soda, and salt together in a medium bowl. Set aside.

Using a hand mixer or a stand mixer fitted with paddle attachment, beat the softened butter and both sugars together on medium speed until creamy and smooth, about 3 minutes. (Here’s a helpful tutorial if you need guidance on how to cream butter and sugar.) Add the egg and vanilla extract and beat on high speed until combined, about 1 minute. Scrape down the sides and bottom of the bowl as needed.

Add the dry ingredients and beat on low speed until combined. With the mixer running on low, add the chocolate chips. Dough will be thick, soft, and sticky.

Transfer the cookie dough to the pizza pan and flatten out with your fingers until it’s around 3/4 inch thick. You do not want it to reach the edges of the pan; keep it thick and centered.

Bake for 20–24 minutes or until puffed and lightly browned on top. Do not over-bake.

Allow the cookie pizza to cool on the pan set on a cooling rack before garnishing/slicing. While the cookie pizza is still warm, I like to press a few chocolate chips into the top. This is optional and only for looks.

Cover leftovers and store at room temperature for 2–3 days or in the refrigerator for up to 5 days.