Start by preheat the oven at hot air program at 250 degrees Celsius.
In a bowl pour the flour, potato flour, baking powder and cacao powder. Mix well.
Mix with an electrical mixer the eggs and the sugar for a few minutes.
While stirring add the dry ingredients.
On a baking sheet place a baking paper.
Pour the batter on the baking paper and place in the middle of the oven for 5 minutes.
Take out the cake and let it rest a few minutes.
Sprinkle some sugar on the cake and flip it upside down on a baking paper. Roll the cake gently in the paper and let it cool down.
While the cake is cooling down make the filling. Start by whip the whip cream and the vanilla sugar to a foam.
Grate the chocolate and mix with the whip cream.
Sprinkle the filling evenly on the cake.
Roll the cake together and let it rest in a cool place until serving time.