Preheat oven at 350°F.
In a large mixing bowl, add flour, cocoa powder, baking soda, salt and icing sugar.
Blend to combine, then add the diced cold vegan butter.
Continue to blend for about 5 minutes or until everything comes together.
Add the vanilla extract and blend on high for 10 seconds to incorporate well.
Transfer the dough onto a piece of plastic wrap or parchment paper and then place another piece over top.
Roll out the dough to about ¼" thick.
Cut the dough with a cookie cutter and place them spaced ½" apart on a parchment lined sheet pan.
Bake for 10-12 minutes.
Transfer them to a cooling rack. Let them cool down.
In a large mixing bowl combine the icing sugar and vegan butter.
Blend until it all starts coming together to a thick paste like dough.
Place this cream mixture on a piece of parchment paper and place another parchment paper on top. Roll it out, and cut it out with the same cookie cutter.
To assemble, place the filling on top of one cookie, and place another cookie on top. Serve and enjoy!