Preparation time: 20 minutes
Baking time: 15 minutes
 

Cookies

1. Preheat the oven to 180° C (350° F).
2. Sift the flour, cocoa, baking soda and salt into a bowl.
3. In a separate bowl, cream the butter and sugar; add the egg and blend well.
4. Add half the dry ingredients and half the milk to the butter mixture and blend well. Mix in the remaining ingredients.
5. Form the dough into small balls and place on a parchment-lined baking sheet; bake for 15 minutes.

Filling and finishing

1. Beat the butter and icing sugar well; add the vanilla.
2. Once the cookies have cooled, spread the inner side of half of them with the filling; use a piping tip for a more professional effect.
3. Top with a second cookie, sandwich style, and refrigerate.