In a medium-sized bowl, mix the cocoa powder, and butter.
Beat in eggs one at a time, until fully incorporated. Mix in the vanilla.
Stir in gradually cookie mix into the wet mixture, add milk and mix until a soft dough forms. Cover bowl with wrap and refrigerate for 3 – 4 hours.
When ready to bake, preheat oven to 350°F. Line cookie sheet or baking tray with parchment paper (baking paper). Roll 1 tablespoon dough into balls for smaller cookies, or 2 tablespoonfuls for larger cookies.
Add the confectioners (icing) sugar to a smaller bowl. Generously and evenly coat each ball of dough in confectioners’ sugar and place onto prepared cookie sheets.
Bake in preheated oven for 12 – 14 minutes. 7. The cookies will come out soft from the oven but will harden as they cool. Allow to cool on the cookie sheet for 5 minutes before transferring to wire racks to cool.