Whisk the flour, cornstarch, salt, baking powder and baking soda in a large bowl.
Beat the butter, brown sugar and granulated sugar in a bowl with a mixer on medium speed until combined but still slightly lumpy (use the paddle attachment for a stand mixer). The biggest lumps should be about the size of small peas; do not overbeat. Beat in the eggs one at a time. Reduce the mixer speed to low; add the flour mixture in batches and beat until combined. Stir in the chocolate chips by hand. Press plastic wrap directly onto the surface of the dough and refrigerate at least 2 hours or preferably overnight.
Preheat the oven to 375 degrees F. Line 2 baking sheets with parchment paper. Drop 2 1/2-inch scoops of dough onto the prepared baking sheets, about 2 inches apart. Bake until the cookies are barely golden around the edges, about 20 minutes, rotating the baking sheets halfway through. Turn off the oven but keep the cookies inside for 5 more minutes to set. Remove the cookies from the oven and let cool 10 minutes on the baking sheets, then transfer to a rack to cool completely.