I made miniature ones, about one inch across, and I think I over-baked them. I also had a slight problem with the eggs whites losing volume as I folded in the pistachio-powdered sugar mixture, so I might try adding a pinch of cream of tartar next time.
Regardless of my small setbacks, I definitely recommend these cookies!
1/3 cup pistachios
3/4 cup powdered sugar
2 large egg whites
1 tbsp sugar
1/4 cup pistachios
1 2/3 cups powdered sugar
1/2 cup softened butter
Preheat oven to 350 F.
Grind pistachios in a food processor with the powdered sugar until fine as dust.
Whisk the egg whites until fairly stiff, sprinkle the sugar over, and whisk until very stiff.
Fold the whites into the pistachio-sugar dust, and combine gently.
Pipe small rounds onto a lined baking sheet using a pastry bag with a plain 1/2" nozzle.
Let them sit 10 minutes to form a skin, then bake for about 10 minutes. They should be set but not dried out.
Remove from the oven and let cool on their sheets.
Grind nuts and powdered sugar in the processor as before, then cream the butter and continue creaming as you add the nut dust. Make sure you have a well-combined soft buttercream.
Then just sandwich the filling between two cookies.