1. In a bowl of a standing mixer, beat the butter and powdered sugar until well mixed.

2. Add the flour and cocoa mix  (Scrap the sides and bottom of the bowl if needed) and beat just until you get a moist dough. 

3. Place the dough in between two large pieces of parchment paper (about the size of a large cookie sheet) and using a rolling pin, smooth the dough to 1/4" thick.

   Allow the dough to cool in the refrigerator for a minimum of 30-45 minutes.

4. Remove the dough from the refrigerator and preheat the oven to 350F.

5. Cut the dough using a 2" square cookie cutter (or your choice of shape and size) and place on a cookie sheet that is lined with parchment paper.

6. Bake in the middle rack for 8-12 minutes. The cookie should look shiny with golden edges.

7. Remove from the oven and wait 10-15 minutes before transferring the cookie to a cooling rack.

To Make the Filling

1. In a bowl of a standing mixer, beat the butter and sugar at high speed.

2. Once the butter a sugar have combine add the tahini paste (start with 2 TBS and add the 3rd if you feel the filling is too stiff) and beat on high for about 5 extra minutes.

Assembling

1. Spread about 1 tsp on the back of a cookie and line another cookie on top.

2. Melt the chocolate chip and shortening and dip the edge of each sandwich cookie. Place on a cooling rack to the firm.