For the sponge cake batter, separate the refrigerator-cold eggs and beat the whites with a pinch of salt in a large bowl until stiff. Just before the egg whites are almost stiff, drizzle about ¾ of the sugar into the mixture. Beat the egg yolks with the remaining sugar until creamy. Combine the flour, starch and baking powder, add to the egg white bowl along with the egg yolks and gently fold or mix together. Smooth the dough mixture on a baking tray covered with baking paper and bake in a preheated oven at 180 – 200 °C top/bottom heat for a good 10 minutes until golden brown.
Then place the sponge dough on a kitchen towel sprinkled with sugar with the baking paper facing up and allow to cool. Clean the strawberries and cut them into fine pieces. Finely puree a good 150 g of them. Whip the cold cream with sugar and vanilla sugar until stiff.
Shortly before the end, add the cream stiffener and the pureed strawberries and mix well again.
Finally, fold in the finely chopped strawberries and chill the strawberry cream. Once the dough has cooled, carefully peel off the baking paper. Now heat the jam and spread it with a brush on the sponge. Allow to cool briefly and spread the strawberry cream evenly on top, leaving the top edge slightly free so that the mixture does not swell out when rolled up. Now, with the help of the kitchen towel, carefully roll up the sponge dough with light pressure.
The roll can now be spread with cream and decorated with strawberries or simply sprinkled with powdered sugar. Good luck and bon appétit!