Step 1

Preheat oven to 350 degrees F. Line two rimmed baking sheets with parchment paper (or silpat mats). If you use parchment paper, give it a light coating of nonstick spray.

Step 2

In a large bowl, whisk together the powdered sugar with the cocoa powder and salt. Whisk in the egg whites (start w/ just two) and vanilla extract and beat just until the batter is moistened. You're looking for a brownie-like, thick and fudgy batter consistency. If it seems too thick, add another egg white-- then a 4th one if it still seems too thick. Then gently stir in the chocolate chips.

Step 3

Spoon the batter onto the prepared baking sheets in 12 evenly spaced mounds per cookie sheet. I like to use a spring-release cookie scoop. Bake about 14 minutes, until the tops are glossy and lightly cracked. Slide the parchment paper (with the cookies) onto wire racks. Let cookies cool completely, and store in an airtight container for up to 3 days.