Beat the eggs with sugar and vanilla sugar until creamy. Then add the baking powder, the sifted flour and the cornstarch and stir until bubbles form.
Grease a baking sheet with butter and cover with baking paper, grease the baking paper with butter again. Spread the dough.
Bake in a preheated oven at 220 ° C for about 10 minutes.
Moisten a kitchen towel and sprinkle lightly with sugar. Overturn the sheet of dough on it, roll it up carefully and let it cool down.
For the filling, whip the whipped cream until stiff and add the sour cream. Beat with the sugar and cream stiffener until completely stiff and put in a cool place. Now roll up the roll and spread the filling. Now cover with fruit to taste and roll up again.