Add to the bowl of a hand mixer confectioners sugar and unsalted butter. Mix to combine flavors about 1 -2 minutes. ( A hand mixer can be used as well)
Blend in the egg and Vanilla extract and mix until fluffy.
In a medium bowl, sift together all-purpose flour, cocoa powder, baking soda, baking powder, and salt. Fold in half the flour/cocoa mixture into the confectioner sugar/butter. Gently combine ingredients.
Add remaining flour ingredients into the sugar mix. Gently fold ingredients together until mixed.
Split dough in half and wrap each piece in plastic wrap and refrigerate at least 2 hours to overnight. At this point, you can freeze the doughs for a later date.
Preheat oven to 375 degrees and line a baking tray with a Silpat or parchment paper and set aside.
Roll the first piece of dough on a flour/cocoa dusted surface to about ½ inch thick. Cut with cookie cutters and place each cookie on the lined baking tray. Space cookies about 2 inches apart and bake for about 7 minutes. (Note 3)
Remove cookies when baked let cool for about 2 minutes. Move cookies to a cooling rack to cool completely. Decorate with icing and sprinkles.