Preheat the oven to 350 degrees F. Line baking sheets with parchment paper or spray lightly with cooking spray.
For the brownie cookie batter: In a medium bowl beat the butter and sugars together until smooth and creamy. Add the egg and vanilla and mix well, until light in color (2-3 minutes).
In a separate small bowl, whisk together the flour, cocoa, soda and salt. Add the dry ingredients to the wet batter and mix until combined. Cover and refrigerate while making the chocolate chip cookie dough.
For the chocolate chip cookie batter
Cream together the butter and sugars until smooth. Add the egg and vanilla and mix well.
In a separate small bowl whisk together the flour, baking soda, and salt. Add the dry ingredients to the wet and gently stir in the chocolate chips.
Portion each type of dough into about 24 equal pieces (so 24 cookie dough balls and 24 brownie balls); they should be small, teaspoon-sized balls.
Gently press together one chocolate chip cookie ball and one brownie batter ball--use your hands to gently form into a cookie shape.
Bake 8-10 minutes (don't over bake). Remove from oven and allow to cool on the pan for 1-2 minutes before removing to a cooling rack.