Preheat oven to 350°F. Spray 2 large baking sheets with nonstick spray.

Place 1 cup of chocolate chips in a microwavable bowl. Microwave for 45 seconds, stir. Heat in 15 second increments, stirring in between, until the chocolate is completely smooth. Let cool for about 10 minutes.

Using electric mixer, beat whites in large bowl to soft peaks. Gradually beat in ½ cup powdered sugar. Continue beating until mixture resembles soft marshmallow creme.

Whisk 1 cup powdered sugar, cocoa, cornstarch, and salt in separate bowl. On low speed, beat the dry ingredients into the egg white meringue. Once it is fully incorporated, add the lukewarm chocolate and ½ cup chocolate chips (optional). Dough will become very stiff. If your dough seems loose at all, I recommend refrigerating the dough for at least a half hour to help it firm up before rolling into balls.

Place ½ cup powdered sugar in bowl. Roll 1 rounded tablespoon of dough into a ball and roll in powdered sugar. Place on baking prepared sheet. Repeat with remaining dough, spacing the cookies 2 inches apart.

Bake until puffed and tops crack, about 10 minutes. Cool on the baking sheets for 10 minutes before transferring to a cooling rack to cool completely.