Preheat oven to 350 degrees F. Line a large baking sheet with parchment paper; set aside.
In a medium bowl, whisk flour, cornstarch, baking soda and salt. Set aside.
In a separate large bowl, or the bowl of your stand mixer fitted with the paddle attachment, beat butter and sugars until light and fluffy. Add egg and vanilla extract. Add flour mixture, mixing until completely combined. Do not over-mix. Fold in chocolate chips.
Roll 2 Tablespoons cookie dough into a ball. Tear ball in half and stack halves on top of each other (like this), placing dough balls 2 inches apart. Press down slightly on each dough ball.
Bake for 8-10 minutes, until edges are slightly golden brown. (The cookies will not look fully baked, but they will resume baking while cooling on baking sheet.)
Remove from oven and let cookies rest on baking sheet for 10 minutes. Transfer to a wire rack to cool completely.