Preheat oven to 370°F. Line a baking sheet with parchment paper. Mix dry ingredients and set aside.
Cream butter with sugars in a mixer in a stand mixer, or with a hand mixer on medium speed. Mix until fluffy.
Add in egg, egg white, and vanilla and mix until well incorporated.
Slowly add combined dry ingredients then chocolate, including the chocolate powder/dust. (It's okay if some of the chopped chocolate cracks in the mixer. It will spread nicely throughout the cookies.)
With a large cookie scoop measuring 1/3 cup in size (or a 1/3 cup measuring scoop), scoop large rounds of the cookie dough onto parchment-lined sheet. Scoop out all the dough into even cookie dough balls of about 1/3 cup in size. You will be freezing all the cookie dough balls on this sheet until solid.
Once cookie dough balls are frozen solid (it will take about 20 minutes), remove and place 5-6 large cookie dough balls on a clean, parchment-lined baking sheet. Return unused cookie dough to freezer - you want to bake these straight from the freezer so they don't spread too much.
Bake for 10 minutes in preheated oven, then remove and gently drop the pan onto the stovetop. This helps get the bakery-style crinkles on the top of the cookie.
Then, return to the oven and bake for 4-6 more minutes until the tops are evenly golden brown.
Once golden brown, remove from oven and gently drop pan one more time on the stovetop, for a couple more crinkles on top.
Sprinkle each cookie with a little flake salt .Let set for 3-4 minutes then enjoy!