Preheat oven to 350 F.
In a bowl, whisk the flour, salt, cocoa and baking powder.
Using a standing mixer or hand mixer in a bowl, cream the sugar and butter for 3-4 minutes until it is light and airy.
Add the egg and orange zest and mix for an additional minute.
Slowly add the dry ingredients into the wet until the dough comes together.
Remove and shape the dough into a flat disk and place between two pieces of parchment paper.*
Roll dough out until it is 1/4 inch thick. Cut into shapes using cookie cutters.
Place cookies on a Silpat or parchment lined baking sheet and bake: 10 minutes if you want your cookies to be slightly soft or 12 minutes if you like them crispy.
Cool and serve.
For the optional icing:
Combine the ingredients in a bowl.
Use to decorate the cookies.
* Dough can be refrigerated for up to 2 weeks at this step.