Unroll the puff pastry together with the baking paper on a baking tray (approx. 35 x 40 cm). Fold both long edges over first about 1 cm to the middle, then again about 4 cm. Slightly cut the edges of the dough with scissors at a distance of about 2 cm. Prick the dough base several times with a fork
Bake in the preheated oven (electric oven: 225 °C/circulating air: 200 °C/gas: level 4) for 10-15 minutes. Let it cool down on the baking tray
Select the berries and wash them if necessary. Whip the sour cream, sugar and vanillin sugar until thick and creamy. Cut dough stripes into 6-7 pieces. Spread the sour cream and berries on top. Dust with icing sugar