MAKES 16 COOKIES
We recommend using the test kitchen’s favorite baking chocolate, Callebaut Intense Dark L-60-40NV, but any high- quality dark, bittersweet, or semisweet chocolate will work. Light brown sugar can be substituted for the dark, as can light corn syrup for the dark, but with some sacrifice in flavor. A spring-loaded ice cream scoop (size #30) can be used to portion the dough.

WHY THIS RECIPE WORKS:
We wanted an exceptionally rich chocolate cookie recipe with a sturdy, not crumbly, texture. The fat in melted chocolate made our dough too soft, so we replaced the chocolate with cocoa powder. Eliminating egg yolks further improved the structure of the cookies. For chewiness, we replaced some of the white sugar in our chocolate cookie recipe with brown sugar and added dark corn syrup. Adding bits of bittersweet chocolate to the dough gave us extra chocolate flavor without compromising the texture we had worked so hard to achieve.

http://www.americastestkitchenfeed.com/bake-it-better/2013/06/secrets-to-chewy-chocolate-cookies/