For the sponge cake roulade with chocolate cream filling, first prepare the cream. To do this, heat the whipping cream in a saucepan and melt the cooking chocolate in it.
Stir the mixture until smooth and cover it with a lid and put it in the refrigerator. Preheat the oven to 200 degrees with top/bottom heat and line a baking tray with baking paper.
Sift the flour into a bowl with the cornflour and baking powder and whisk to incorporate. Beat the eggs in a mixing bowl, add the water and beat both for a few minutes until foamy.
Meanwhile, slowly sift in the sugar and vanilla sugar. Finally, gently fold in the flour mixture. Spread the finished dough on the baking sheet and smooth it out. Bake on the middle shelf for about 15 minutes.
In the meantime, line a large cotton cloth and sprinkle with sugar. After the baking time, remove the sponge cake and immediately turn it out onto the cloth. Carefully peel off the baking paper.
Now roll up the sponge cake with the help of the cloth and let it cool completely. Then roll it out again. Whip the cooled cream mixture with a mixer, spread it on the dough and roll it up into a sponge roulade.
Sprinkle the sponge roulade with chocolate cream filling with powdered sugar, if desired.