Beat the egg and softened butter until frothy, then add the sugar, vanilla sugar and a pinch of salt and stir in. Add the baking soda and gradually stir in the flour. Finally fold in the chocolate. (I used the already roughly chopped Dr. Oetker chocolate.)
To get the round shape of the cookie, you can take a cake tin, add the dough and smooth it out. Remove shape.
Bake the cookie at 160 degrees air circulation for about 5 - 9 minutes. Depending on how juicy / fudgy or crispy you like it.
After baking, carefully lift off the baking sheet and let cool down a little.
Serve the still warm cookie with vanilla ice cream and the wafer rolls.