Preheat the oven to 350° F. Line a cookie sheet with parchment paper or a silicone liner and set aside.
Add the softened butter, brown sugar and granulated sugar to the bowl of a stand mixer or into a large bowl if using an electric hand mixer.Mix until well combined and creamy.
Slow the mixer down to low and while the mixer is still going, add in the egg, corn syrup and vanilla.
Stop the mixer and add in the flour, cocoa powder, corn starch, salt and baking soda. Mix until all of the ingredients are incorporated. The dough will be quite soft but shouldn’t stick to your hands.
Scoop and roll the dough into a ball. For small cookies use a #40 scoop or 1 1/2 tbsp of dough, for larger cookies use a #24 scoop or 3 tbsp of dough.
Roll into a ball and then press the top of the ball into a bowl containing mini chocolate chips and then arrange on your baking sheet. Repeat with remaining dough.
Bake at 350° F until the cookies spread and the edges of the cookie start to crackle. For the smaller cookies, 8-10 minutes. For the larger cookies, 11-13 minutes.
Allow the cookies to cool for 5-10 minutes on the pan before transferring to a wire cooling rack. Store in an airtight container for up to 3 days.