In a medium bowl, whisk together the flour, cocoa powder, flax meal, coconut sugar, and salt. Mix well.
Add 2 Tablespoons solid coconut oil, the vanilla, and the Stevia to the dry mixture and mix together until mixed well and a dough forms. If the dough seems dry, you can add milk 1 Tablespoon at a time. You can knead the dough at this point if needed.
Shape the dough into a round log 1 inch in diameter. Wrap the dough with parchment paper or plastic wrap and refrigerate until firm, about 30 minutes to 1 hour.
Preheat oven to 350 degrees.
Once the dough has chilled and is firm, slice the dough into 1/8-inch thick slices and place on a cookie sheet.
Bake for 10-15 minutes or until well set. If you want a crispier cookie, bake another 5 minutes or so.
Cool completely on a wire rack.
Meanwhile, put 1/4 cup coconut sugar in a small blender or food processor. Pulse process the sugar until it is powdered fine, about 30 seconds.
Mix the powdered coconut sugar, the solid coconut oil, and the vanilla together until well mixed.
When the cookies are cooled completely, spread the filling between two cookies and enjoy!