Place oven racks in lower and upper thirds of oven, and pre-heat to 350 degrees. Line two baking sheets with silicon pads (Silpat) or parchment paper. Sift together the powdered sugar, cocoa powder, expresso and salt into a large bowl. Whisk well to combine. Then whisk in the egg whites, whole egg and vanilla. Fold in the chopped chocolate. Don’t overmix the batter, it will thicken as it sits.