Preheat oven to 350° F.
Using a stand mixer or an electric hand mixer, cream together the salted butter, brown sugar and granulated sugar until light in color and fluffy in texture.
Scrape the sides and add the eggs and vanilla. Mix until well combined.
Add the flour, cocoa powder, cornstarch, baking soda and salt. Mix until a soft dough forms.
Lastly, add in the chocolate chips, mixing until evenly distributed.
Use a #40 scoop to portion out the dough into equal 1 1/2 tbsp of dough.
Roll into a ball and flatten slightly. Press some extra chocolate chips onto the tops of the cookie dough, if desired.
Bake at 350° F for 7-9 minutes, or until the cookie no longer looks wet and glossy on top and the cookie has spread some.
Allow the cookies to cool on the pan. Store in an airtight container for up to 4 days.