Preheat oven to 350°F. Line a baking sheet with parchment paper and lightly coat with non-stick cooking spray.
In a large bowl, whisk powdered sugar, cocoa, and salt. Add egg whites and vanilla and beat with a wooden spoon until smooth. Fold in chocolate chips. Refrigerate for 5 to 10 minutes until slightly thickened.
Drop dough by rounded tablespoonfuls, 2 inches apart, onto prepared cookie sheet. Bake 13 to 15 minutes, or until set and the tops have some cracks on them. Let cool for 5 to 10 minutes before serving.