"These are my favorite chocolate chip cookies. They're soft, tender, moist, with pillowy centers and chewy edges. There's a secret ingredient, which keeps them super soft and tender: cornstarch. I use two types of chocolate in them; chocolate chips and chocolate chunks, for extra depth and flavor. Feel free to make this dough in advance, refrigerate it, and bake it off up to 5 days later for fresh hot cookies exactly when you want them...."