Mix brown sugar, granulated sugar, butter, egg, egg yolk salt and vanilla essence in a large bowl until well mixed.

Stir in flour, cocoa powder, baking powder, salt and baking soda until blended (dough will be soft and creamy).

Divide dough into three equal portions. Wrap each portion with plastic wrap and transfer to refrigerator, let chill for 30 minutes.

Unwrap the chilled dough and place on a lightly floured work surface (I dust my surface with cocopowder).Roll out to about 1/2-1 inch thick.

Sprinkle with half the chocolate chips on top of the first portion of chilled dough. Roll out the second dough ball and set on top. Sprinkle with remaining chocolate chip and to and then set the final portion of dough on top of that.

Gently flatten with rolling pin and try create a square the cookie dough you can fold the dough over it self and roll the cookies again of desired.

These cookies don't rise very much so that make sure your dough is the desired thickness of the final cookies before moving on to the next step.

Cut dough into 2 inch squares with a sharp knife and set on a cookie sheet lined with parchment paper about an inch part.

Bake at 350°F for 11-14 minutes. After baking Couple a minute rest on baking sheet and the transfer to a wire rack to cool completely.