2 3/4 cups walnut halves
3 cups confectioners’ sugar
1/2 cup plus 3 tablespoons unsweetened cocoa powder
1/4 teaspoon salt
4 large egg whites, at room temperature
1 tablespoon pure vanilla extract
Preheat oven to 350.
Line two large-rimmed baking sheets with parchment paper.
In a large bowl, whisk (or combine in an electric mixer on low speed) the confectioners’ sugar with the cocoa powder and salt followed by the chopped walnuts. While whisking (or once you change the speed to medium), add the egg whites and vanilla extract and beat just until the batter is moistened (do not overbeat or it will stiffen).
Spoon the batter onto the baking sheets in 12 evenly spaced mounds, and bake for 14 to 16 minutes, until the tops are glossy and lightly cracked; shift the pans from front to back and top to bottom halfway through to ensure even baking. Slide the parchment paper (with the cookies) onto 2 wire racks. Let cookies cool completely, and store in an airtight container for up to 3 days.