In a mixing bowl of a stand mixer, cream together butter and sugars on high speed until light and fluffy (about 3-4 minutes). Add eggs one at a time, mixing well after each addition.

Add in cocoa, cake flour, all-purpose flour, cornstarch, baking soda, and salt and set mixer on lowest speed setting to stir until dough is just combined (please note in the video the mixing is sped up to keep the video short). You want the dough to be smooth and uniform in color, but you don't want to overmix it. Stir in chocolate chunks.

Place the dough in the fridge for 15 minutes to chill.

Line two baking sheets with silicone baking mats. Measure out about 4.3 oz of dough and roll into a ball. Place several chocolate chips on top and adjust chips until the dough weighs 4.5 oz. Place dough ball onto baking sheet. You will place four on each baking sheet, spaced about 2 inches apart. You should have enough dough to make 8 cookies, but it is best to weigh the balls so that they are all the same size and will cook evenly.

Bake the cookies for about 10-11 minutes, or until the surface is dry and cookies look almost set. Remove and let cookies cool on the baking sheets (if you try to remove them they will likely break apart). Allow cookies to cool about 15-20 minutes so that they can set. Then remove and enjoy.