Preheat oven to 350 and line 2 baking sheets with silicone baking mats or parchment. Spray the mats or parchment with non-stick spray.
In a large bowl, sift powdered sugar and cocoa powder. Whisk in salt. Add egg whites and vanilla and whisk until combined and batter is smooth (this requires some muscle). Fold in chocolate chips and almonds.
Using a medium size cookie scoop, portion out 8 cookies on each baking sheet (they do spread out, so I don't recommend putting more than 8 on the sheet at a time). Press 5 marshmallows into the top of each cookie. ***[See notes here]
Bake for 14 minutes or until cookies are crisp and set but gooey on the interior.
Allow to cool at least 5 minutes before removing to cooling rack to cool completely. Remove carefully.