Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper to prevent the cookies from sticking.
In a large mixing bowl, use an electric mixer to whip the egg whites until they form soft peaks.
In a separate bowl, whisk together the powdered sugar, cocoa powder, and salt until well combined.
Gently fold the dry ingredients into the whipped egg whites using a rubber spatula.
Stir in the vanilla extract and the roughly chopped dark chocolate until evenly distributed throughout the batter.
Using a spoon or cookie scoop, drop tablespoon-sized portions of dough onto the prepared baking sheet.
Bake in the preheated oven for about 12-15 minutes, or until the cookies are set around the edges and slightly soft in the center.
Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
