For the sponge cake, separate the eggs. Whip egg whites, water (1) and salt until stiff.
Add 2/3 of the sugar and half of the vanilla sugar.
Fold in all the egg yolks. Combine flour and baking powder, sift onto egg mixture and fold in. Spread the dough onto a baking tray lined with parchment paper and bake in a heated kitchen oven (electric oven 200 °C /gas mark 3) for approx. 12 minutes. Turn the sponge out onto a damp tea towel sprinkled with sugar. Remove the parchment paper. Spread the sponge on the spot with the jelly, roll up and cool. Soak the gelatine. Rinse and select raspberries. Crush 2/3 of the raspberries and pass through a sieve. Press on gelatin, let it melt and stir it into the puree. Set aside to cool. Whip the cream, remaining sugar and vanilla sugar until stiff. As soon as the puree begins to firm, fold in whipped cream first, then remaining raspberries. Cut roll into twice as many pieces as it should cut shape. Spread raspberry cream evenly on half of the slices. Top with remaining slices and refrigerate about 1 hour. Dust with powdered sugar and bring to table.