Preheat the oven to 350 degrees.
Line the cookie sheets with parchment paper.
Combine flour, cocoa, cornstarch, baking soda, and salt in a large bowl.
3 ¾ cup all-purpose flour, 1 cup cocoa powder, 2 teaspoon baking soda, 1 teaspoon Kosher salt
Whisk to mix. Set aside
Cream together in a large mixing bowl the butter, white and light brown sugar using an electric mixer until it becomes light in color and fluffy.
½ cup sweet cream butter, ½ cup light brown sugar, ½ cup white granulated sugar
Add in the three eggs, pure vanilla, and corn syrup mixing until completely mixed.
3 large eggs, 1 Tablespoons pure vanilla extract, 2 Tablespoons light corn syrup
Continue beating while adding in the flour mixture until a soft cookie dough begins to form.
With a large ice cream scooper, scoop dough into your hands and roll into a ball
Place on the cookie sheet about 2 in apart from the other dough
Use your hands to flatten the dough into the same size circles.
Bake for 15-17 minutes.