Preheat the oven to 350°. Line you baking sheet with parchment paper or a silicone baking mat. Set aside.
In the bowl of a stand mixer or with an electric hand mixer, cream together the margarine, butter, brown sugar and sugar until well combined.
Scrape the sides of the bowl and add in the egg, corn syrup, molasses and vanilla extract. Mix until combined.
Add the flour, cocoa powder baking soda and salt, mix until the dough forms.
Mix in the chocolate chunks.
Portion the dough out into approx 2 1/2 tbsp portions. I use two scoops from my #50 scoop for each cookie. Roll into a ball and place on the prepared baking sheet. Repeat with the remaining dough.
Bake at 350° for 11-13 minutes. The cookie will flatten, spread and the edges should start to crack when they are ready to come out of the oven.
Allow the cookies to cool on the pan for 5 minutes before transferring to a wire cooling rack.
Store in an airtight container at room temperature for up to 3 days or in the freezer for up to 3 months.