Preheat oven to 400 degrees.
Spray 2 baking sheets with nonstick spray or line with parchment paper.
Melt 1 cup chocolate chips in microwave for 2 minutes, stirring every minute. Cool slightly.
Using a mixer, beat egg whites until soft peaks form. Gradually add 1 cup sugar. Continue beating until mixture looks like marshmallow cream.
In a separate bowl, whisk together cocoa, sugar, cornstarch and salt.
On low speed, beat dry ingredients into egg white mixture. Stir in melted chocolate and 1/2 cup chocolate chips. Dough will be very stiff.
Roll into 1 tablespoon balls. You can roll them in additional powdered sugar if desired.
Place on cookie sheets about 2 inches apart.
Bake until puffed and tops are cracked, about 8-10 minutes, but don’t overbake.
Cool on sheets for 10 minutes, then transfer to a rack to cool.