1/2 - 3/4 cuppowdered sugar for rolling prepared dough in
Preheat oven to 340° F. Line a cookie sheet with parchment paper or Silpat mat.
Cookie Dough Prep
In a small bowl, combine brown sugar, powdered sugar, cocoa powder, espresso powder, and salt. Set aside.
In a small bowl, beat the egg yolks slightly. Set aside.
In a food processor, pulse walnuts until they resemble cracked wheat. [Be careful - if you let them go too long, you'll have walnut butter!] Measure walnuts after chopping. Set aside.
Melt chocolate in a glass bowl in the microwave for 40 seconds at a time, stirring after each cycle, until chocolate is completely melted. Allow to cool slightly.
Using an electric mixer, beat egg whites until they form stiff peaks. To the beaten egg whites, gradually add brown sugar mixture and then vanilla, beating until thick. Gently fold in walnuts and beaten egg yolks.
Fold the melted chocolate chocolate into the whipped egg-white mixture.
Refrigerate dough for at least 3 hours, or overnight. [DO NOT attempt to make cookies until the dough is cold!]
Form 1" balls of dough using a small cookie scoop or spoon. (About 2 teaspoons per cookie.) A small cookie scoop works perfect for this.
Pour 1/2-3/4 cup powdered sugar into a shallow bowl or plate. Rolls cookie dough balls in powdered sugar. Place cookie balls on prepared cookie sheet, about 2 inches apart. (You do not need to press the cookie balls down.)
Bake in preheated oven for 10 minutes. (If you make your cookies larger, you may need to bake them for an addition 2-3 minutes.) Remove from oven and allow to cool for 5 minutes before moving to a cooling rack.
Walnuts should be chopped very fine, but not beyond recognition - about the same consistency as cracked wheat.
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