Preheat your oven to 375° F (190° C) and position your rack in the middle of the oven. Line a cookie sheet (half-sheet pan) with parchment paper for the best results, I usually use 3 cookie sheets. Beat the softened butter until light and fluffy, about 1 minute. Add both sugars and continue beating until creamed and smooth, between 3-5 minutes, scraping down the sides of the bowl about halfway through. (You may use a hand mixer, but I believe a stand mixer does a better job creaming the butter and sugars here) Add eggs one at a time, mixing on medium speed, 1 minute per egg — then mix in the vanilla. Scrape the sides of the bowl to mix the ingredients completely. In a medium bowl, combine the dry ingredients; flour, baking soda, corn starch and salt and whisk well to combine. With mixer on low speed, add the flour mixture to the wet ingredients, a little at a time. Mix just until combined and there are no more visible streaks of flour. For the best results DO NOT OVERMIX if you want chewy, soft cookies. Add the chocolate chips. You can either fold them in by hand or use the lowest setting on your mixer. Scoop out a heaping ⅓ cup of cookie dough (4.2 ounces/117 grams if you are geeky like me) and pinch the dough ball in half, turning the top off upside down on top of the bottom of the half, jagged side up. Place cookie dough ball 2-3 inches apart on prepared baking sheets. I used a large cookie scoop. This is a no chill cookie recipe, however; if your dough is really really soft, due to heat, humidity, too soft or water of butter, then I suggest chilling the cookie dough in the refrigerator for 10-20 minutes before baking. Bake for 10-12 minutes, and not a minute longer! The cookies should be just barely golden at their edges and slightly firm in the center. Leave them to cool on the pan for 10 minutes, then move them to a wire rack to finish cooling. Store cookies in airtight container on counter. May be frozen up to 3 months. To freeze dough balls, place dough balls on tray and flash freeze for one hour until firm, then transfer to an airtight container and freeze up to 3 months. Bring dough balls to room temperature before baking.