How to Make It
Preheat oven to 350°F. Sift together powdered sugar, cocoa, and salt in a large bowl.
Whisk egg whites until frothy. Stir egg whites and vanilla into powdered sugar mixture. (Batter will be very thick.) Stir in chopped chocolate and pecans until well combined.
Drop cookies 3 inches apart using a 1 1/2-inch cookie scoop (about 2 tablespoons) on a parchment paper-lined baking sheet lightly greased with cooking spray.
Bake in preheated oven until tops are shiny and cracked, 8 to 10 minutes. Cool on baking sheet 5 minutes; transfer to wire racks, and cool completely, about 15 minutes.