In a bowl, whisk together the flour, cocoa powder, salt, baking powder and instant espresso powder, set aside.
In the bowl of a standing mixer fitted with a paddle attachment, cream together the butter and sugar, add the vanilla and eggs and mix until creamy and smooth.
Add the dry ingredients and mix them in long enough to combine.
Place the dough in a bowl, cover and refrigerate for a minimum of 3 hours or up to overnight.
Preheat your oven to 350 degrees, line a couple baking sheets with parchment paper and set aside.
Using a small ice cream scoop or two spoons, form little balls of dough and coat them in the powdered sugar, place them a couple inches apart on your prepared baking sheets.
Bake the cookies for 10 to 12 minutes and allow them to cool completely before serving.