Line two baking sheets with parchment paper. Spray the parchment paper lightly with cooking spray.
In a large bowl, whisk together the powdered sugar, cocoa powder, salt, cornstarch & baking soda
Beat in two egg whites and the vanilla extract and vinegar and food coloring until the batter is moistened.
The consistency should be a thick and fudgy batter. As all eggs are not created equal, if the batter seems too thick, add another egg white or two.
Add the chocolate chips and salt and mix to combine.
Spoon batter onto the prepared baking sheets in 2 inches apart.
Bake about 12 - 14 minutes, until the tops are shiny and lightly cracked.
Slide cookies on the parchment paper onto wire racks and let cool completely.
For a truly gluten-free treat, be sure to choose ingredients that are certified gluten-free. Some brands of cornstarch, chocolate chips, and confectionary sugars have starch that contains gluten. So read the packages carefully.
Let the cookies cool a few minutes before serving them. They tend to fall apart when very hot.
If you don’t have chocolate chips, feel free to use finely chopped chocolate from a bar.