1cupconfectioner's sugar or icing sugarfor coating
In a stand mixer or in a large-sized bowl with a hand mixer, mix together white sugar and butter for 3 minutes on high speed. Beat in eggs one at a time, until fully incorporated. Add the hazelnut liquor.
On slow speed add the cocoa powder, salt and baking powder until incorporated.
Add the flour and mix until a dough forms (do not overbeat). Cover bowl with wrap and refrigerate for at least 4 hours or overnight. The dough will be sticky.
When ready to bake, preheat oven to 350°F.
Line 2 cookie sheets with parchment paper (baking paper or a silpat sheet). Roll 1 tablespoonful of dough into balls for smaller cookies, or 2 tablespoonfuls for larger cookies.
Add the confectioner's 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 350-degree oven for 10 minutes (for small cookies) or 12 minutes (for larger cookies).
The cookies will come out soft from the oven but will harden up as they cool.
Allow to cool on the cookie sheet for 5 minutes before transferring to wire racks.
Store in airtight containers to prefent the cookies from hardening.
If you don't want to use hazelnut liquor, you can substitute 2 teaspoons of hazelnut extract to the mix instead!