Bring the cherries, sugar, kirsch, cinnamon and vanilla sugar to the boil in a saucepan over low heat. Mix starch with 4 tablespoons of water, pour it to the cherries while stirring, let it simmer for about 1 minute, remove from the stove. Let the cherries cool down for about 30 minutes
Let the strudel dough rest in the closed package for about 10 minutes at room temperature. Melt butter. Put the lady fingers in a freezer bag and crumble finely with a cake roll. Stir 3 tablespoons of the crumbs into the cherries
Spread a tea towel on a work surface. Remove the strudel dough from the package. Place 1 sheet of dough on the towel, spread a thin layer of butter on it. Place the remaining sheets of dough one after the other, turned by 90°, on the cloth, brushing each sheet with a thin layer of butter
Sprinkle the dough with the remaining sponge crumbs. Place the cherries on a narrow side, leaving an approx. 2 cm wide rim on the sides and on the narrow side. Press the cherries carefully flat. Fold the side edges inwards
Using the cloth, roll up the cherries from the narrow side into a strudel. Place the roll of dough with the seam facing down on a baking tray (32 x 38 cm) lined with baking paper. Spread the strudel with some butter
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 40-45 minutes. Brush with remaining butter from time to time. Remove the strudel, let it cool down for about 15 minutes, cut into pieces and dust with icing sugar
Waiting time approx. 30 minutes