Take the puff pastry out of the fridge and let it rest for 5-10 minutes. Unroll the dough on a baking tray (34 x 39 cm) with the rolled up baking paper (shorten the dough 2-3 cm if it is too long). Score lengthwise with a sharp knife. Then carve into each half in 9-10 cake pieces. Mix egg yolk and 1 teaspoon cold water, spread a thin layer of puff pastry with it. Sprinkle one row of cake pieces with sugar crystals.
Bake in the preheated oven, bottom shelf (electric oven: 225 °C/ convection oven: 200 °C/ gas: level 4) for 10-15 minutes. Let them cool down. Only fill the puff pastry shortly before serving. Soak, squeeze and dissolve the gelatine. Mix with rum. Whip cream, sugar and vanillin sugar until stiff. Finally add the rum mixture and fold in. Chill the cream. Cut the puff pastry sheet lengthwise and cut the cake pieces sprinkled with sugar crystals apart. Spread the pieces from the other half each with approx. 1 tbsp. plum jam.
Whip cream, sugar and vanillin sugar until stiff. Finally add the rum mixture and fold in. Chill the cream. Cut the puff pastry sheet lengthwise and cut the cake pieces sprinkled with sugar crystals apart. Spread the pieces from the other half each with approx. 1 tbsp. plum jam. Put the cream into a piping bag with a large perforated spout and squirt some cream on each piece. With the remaining cake wings
Waiting time approx. 30 minutes