Put half of the sugar and the cornstarch in a small bowl. Add the egg yolks and 1/4 of the milk and mix everything well with a whisk.
In the meantime, bring the rest of the milk with the rest of the sugar and the vanilla sugar to the boil. Slowly pour the egg mixture into the boiling milk while stirring. If the cream has boiled properly a few times and a homogeneous mass has formed, remove it from the stove immediately. Now stir the coffee powder into the cream. Let the mocha cream cool down, being careful not to skin it. As soon as it has cooled, fold the whipped cream into the cream.
Now fill the finished mocha cream into a large glass bowl or into small portion bowls, dust with cocoa powder and decorate with wholemeal cookies. Place in the refrigerator until ready to serve.