Place puff pastry sheets next to each other and allow to thaw. Place the puff pastry sheets on top of each other. Roll out to a square of 32 x 32 cm on a floured work surface. Let rest for 10 minutes. For the topping, wash and stone the plums, cut them into slices and simmer with 100 g sugar and 100 ml water for 5 minutes.
Remove 2 tablespoons of plum wedges for decoration. Mix starch with 3 tablespoons of water, stir into the remaining plums and bring to the boil. Leave to cool. Place the dough on a baking tray lined with baking paper.
Place the edge of a springform pan (28 cm Ø) in one corner of the pastry sheet and cut out a circle, brush with water and prick several times with a fork. Cut dough remains into two 4 cm wide strips.Mix 1 tablespoon sugar and cinnamon.
Spread the strips of dough with butter and sprinkle with the cinnamon sugar. Roll them up in an "S" shape, cut them into slices about 1 cm wide and place them on the baking tray. Bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 20 minutes.
For the topping, puree the marzipan with 200 g whipped cream. Whip the remaining cream and sugar until stiff and fold in. Pour the plum compote and marzipan cream one after the other onto the cooled dough plate.
Decorate the cake with remaining plums and the baked "S".