Add butter and sugars to the bowl of a stand mixer. Beat with paddle attachment until light and fluffy, about 2 minutes. Add vanilla and combine. Add eggs one at a time until mixed through.
In a separate bowl, combine cocoa powder, flours, cornstarch, baking soda, and salt together until combined. Add all of the mixture to the butter-egg mixture. Beat just until combined. Add chocolate chips and chocolate chunks. Beat until evenly dispersed, only about 5 seconds.
Scoop balls of dough with a 1 1/2 to 2 tablespoon cookie scoop. I used a 1 tablespoon scoop and heaped it. Roll each ball of dough into a perfect sphere. Place onto large platter or baking sheet. Repeat with rest of the dough. Chill in the fridge for about an hour.
Preheat oven to 375 degrees. Remove cookie dough from fridge to sit at room temperature while the oven preheats. At this point, decide if you want rounded cookies or flat ones. If you want rounded, keep them in the rounded shape. If you want flatter ones, slightly flatten with the bottom of a cup or mug. Transfer to a baking sheet, if not already on one. Leave about 2 inches between each cookie.
Bake cookies in a preheated oven for 8-9 minutes, just until the bottoms start to crack slightly. These cookies are better under-cooked so don't cook for more than 9 minutes. Let them site for 10 minutes to set up. I love love love these cookies warm from the oven so I suggest serving immediately. But you can also warm them up in a microwave later on (5-8 seconds max).