Start to whip the egg whites with the pinch of salt and once they become foamy, slowly add the sugar and vanilla sugar (or extract). Whip until egg whites keep their shape.
Mix the flour with the cocoa powder. Through a sieve, give the mixture on top of the egg whites.
Carefully fold the dry ingredients into the egg whites until well combined.
Fill the batter into a piping bag with a medium-sized round tip.
Prepare two baking sheets with parchment paper or a silicone mat.
Pipe the batter onto the baking sheets in the shape of letters and numbers.
Let the letters and numbers dry for about 20 minutes, meanwhile, preheat the oven to170°C / 340°F.
Bake the cookies for about 16 to 18 minutes – it might be less or more time, depending on your oven – check oven in between and make sure you don't bake them too long! Remember: The cookies will continue to bake after you took them out of the oven!
