line two baking sheets with parchment paper and spray with nonstick spray
preheat oven to 350 degrees
in a large bowl, whisk together cocoa powder, powdered sugar & salt (optional)
stir in egg whites & vanilla extract until the batter is completely moistened – it will be very thick – if it seems too think, add another egg white
gently stir in the chocolate chips
spoon the batter on the parchment paper lined baking sheets – leave enough space between because each cookie will spread a bit
bake for 12-14 minutes, until the tops are glossy & begin to crack
let cookies cool completely before removing from baking sheets