IN a large bowl whisk together the powdered sugar with the cocoa powder and salt.
Whisk in vanilla and 2 egg whites.
Beat just until the batter is moistened. You are looking for a brownie-like consistency in the batter. Add additional egg whites until you reach that consistency; I used all 4.
Stir in chocolate chips.
Scoop the batter by the tablespoonfuls onto the prepared baking sheets. Leave plenty of space for each cookie to spread.
Bake for 12 - 14 minutes or until the tops are glossy and lightly cracked.
Let the cookies cool completely on the baking sheet and then store in an airtight container for up to 3 days.