Similar in texture to a Russian tea cake or Mexican wedding cookie, nan-e gerdui are small shortbreads made primarily from ground walnuts and rice flour, a combination that makes a cookie that's crumbly on the outside and slightly chewy within.
Combine the all-purpose flour, rice flour, and walnuts in the bowl of a food processor and process until the walnuts are a fine powder. Whisk in the cardamom and set aside.
Beat the butter, salt, and confectioners’ sugar together in the bowl of a stand mixer until fluffy, about 3 minutes. Add the rose water and mix for another 30 seconds until totally combined.
Add the flour and walnut mixture in two stages, mixing until thoroughly combined after each. Scrape the dough into a bowl, cover, and chill for 30 minutes.
Preheat the oven to 400°F. Line a baking sheet with parchment.
Using a teaspoon cookie scoop, scoop the dough onto the prepared baking sheet, placing the balls 1 1/2" apart. Using a rubber spatula, press the dough balls lightly to flatten slightly into thick little circles. Garnish each cookie with a pinch of ground pistachio.
Bake the cookies for 12 to 14 minutes, or until just firm to the touch; don't allow them to brown around the edges. Remove from the oven and cool right on the pans for 10 minutes before transferring to a rack to cool completely.
Store cookies, well wrapped, at room temperature for several days; freeze for longer storage.
