In a medium bowl, combine the flour, cardamom, orange zest and salt. Set aside.
Using a stand mixer fitted with a paddle attachment or hand mixer on the medium-high setting, beat together butter and sugar until light and fluffy, about 2 minutes. Mix in the egg and almond extract. Reduce the mixer speed to medium-low and add the flour mixture, mixing until just combined. Fold in the pistachios with a spoon or spatula.
Place the dough on a sheet of plastic wrap, shape into a 2 x 12-inch (5 x 30-cm) log and wrap tightly with the plastic wrap. Refrigerate for 30 minutes or until firm and chilled through.
Preheat oven to 350ºF (175ºC) and line a baking sheet with parchment paper. Remove the dough from the plastic wrap and slice into ⅓-inch (8-mm) thick slices. Place the slices onto the prepared baking sheet, 1 inch apart, and bake for 13 to 15 minutes, until slightly golden on the edges. Transfer to a cooling rack and allow to cool to room temperature.
In a small, wide bowl, slowly whisk the milk, 1 tablespoon (15 milliliters) at a time, into the powdered sugar until just thin enough to coat the tops of the cookies. If too thick, add a little more milk. If too thin, whisk in a little more powdered sugar. Dip the top of each cooking into the glaze, dripping off any excess. Top with decorating sugar or ground pistachios. Allow to set before storing in an airtight container.