Preheat the oven to 350°F. Line 2 cookie sheets with parchment paper.
In a medium bowl, flour, cornstarch, baking soda, and salt; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and both sugars on medium speed until light and fluffy, about 2 minutes. Scrape down the sides of the bowl then add the egg and vanilla and beat until well combined. Add half of the flour mixture and mix for 15 seconds. Add the remaining flour mixture and beat until just incorporated. Fold in chocolate chips.
Drop by rounded tablespoons onto prepared baking sheet, leaving about 2 inches between them. Bake for 8-10 minutes or until barely golden brown around the edges. Let cookies cool on sheets for 5 minutes before transferring cookies to wire racks to cool completely.