- 3 cups confectioners' (powdered) sugar (if you have corn sensitivities, make sure you use corn-free powdered sugar!)
- 1/2 cup plus 3 Tbsp unsweetened cocoa powder
- 1/4 tsp salt
- 4 large egg whites, at room temperature
- 1 Tbsp pure vanilla extract
Preheat oven to 320°F. 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. 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 over beat or it will stiffen).
Spoon the batter onto the baking sheets in 12 evenly spaced mounds, and bake for 14-16 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 (I only did one pan at a time and I have a newer oven that cooks pretty evenly, so I didn't do this). Slide the parchment paper (with the cookies) onto 2 wire racks. Let cookies cool completely. Store in an airtight container for up to 3 days.