Heat oven to 350F and line a rimmed baking sheet with parchment paper.
Brown the butter by melting it slowly in a small saucepot. Remove from heat once the butter just begins to turn a golden color. Pour into a medium sized bowl to cool slightly.
Pulverize the powdered sugar, nuts, and flour together in a food processor until the nuts feel fine. Stir into the melted butter and mix until just combined. Let this sit and cool for a few minutes. Scoop onto cookie sheet and bake 10-12 minutes. Once your cookies have cooled for 10 minutes (but still warm to the touch), roll them in powdered sugar.