Finely grate the marzipan. Stir the sour cream and marzipan with the whisk of the hand mixer until smooth. Wash and halve the plums, remove the stones. Cut the flesh into very fine slices
Unroll the puff pastry on the baking paper. Prick several times with a fork. Spread evenly with marzipan cream. Cut into 15 strips (approx. 2.5 x 25 cm). Pull the strips slightly apart
Place the plum slices close together on each strip so that the arch of the plum slices protrude uniformly on one long side for 1-2 mm. At the end of each strip of dough, leave an approx. 1.5 cm wide edge
Carefully roll up each strip of dough tightly. Press the free end gently. Place the plum roses carefully on a baking tray lined with baking paper
Whisk the egg yolk and 1 tablespoon of water. Carefully brush the edges of the plum roses with it. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 20-25 minutes
Remove from the oven, place on a cake rack, dust with icing sugar and allow to cool. Carefully remove from the baking paper. Arrange on a plate. Serve with vanilla sauce