Sorry to disappoint, but the secret ingredient isn't anything exotic or special: it's just cornstarch. Yes, cornstarch. If you like your cookies to have that crispy exterior but still have a chewy interior, then this recipe is for you. It's the cornstarch that lets that happen. That's how I like my cookies and this recipe has fast become a family favourite. You can use regular chocolate chips in these, but it really is worth it to chop up some great chocolate instead. Thanks to Anna Olson of the Sugar tv show for the great tip.