Combine all of the dry ingredients: almond flour, flax meal, cocoa powder, ground chia seeds, Erythritol, baking soda and salt in a bowl.
In another bowl mixed with mixer soft butter and egg.
Slowly add dry mix and beat until sticky dough. Place the dough on a film and refrigerate for a minimum of 2 hours.
Preheat the oven to 350°F. Line the baking sheet with a silicone non-stick mate. Dust the table surface with cacao powder. Roll out the dough until thin ½ cm thick. Cut out the cookies using a round cutter.
Gentle transfer the cookies on a silicon matt and bake for 8-10 min. Remove and let them cool for 1 hour.
Prepare the filling: In a bowl beat the softened butter, Erythritol, vanilla extract, and coconut oil.
Place approx. 1 tbsp of the filling on one of the cookies and press another cookie on top.