Makes 30 cookies
3 cups confectioners' sugar
2/3 cup unsweetened Dutch-processed cocoa powder
1/8 teaspoon salt
1 tablespoon pure vanilla extract
2 to 4 large egg whites, at room temperature
1 1/2 cups semi-sweet chocolate chips
Preheat the oven to 350 degrees.
Set aside two baking sheets lined with parchment paper.
In a large bowl, whisk the confectioners' sugar, cocoa powder and salt until blended.
Whisk in the vanilla and egg whites starting with just 2. Beat just until the batter is moistened. You're looking for a brownie-like, thick and fudgy batter. If it seems too thick, add another egg white ? then a fourth one if it still seems too thick.
Stir in the chocolate chips.
Scoop tablespoons of the batter onto the prepared baking sheets. Leave enough space between each cookie for them to spread, and avoid making them too big or they will be tough to remove from the parchment paper.
Bake for 12 to 14 minutes, until the tops are glossy and lightly cracked.
Slide the parchment paper (with the cookies) onto wire racks. Let cookies cool completely, remove from parchment paper and store in an airtight container for up to 3 days.