Place the puff pastry slices next to each other and let them thaw for about 10 minutes. In the meantime whisk the egg yolks and milk. Cut the puff pastry squares in half. Place on three baking trays lined with baking paper. Brush all of them with egg yolk and milk and sprinkle half with sugar crystals. Bake one after the other in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 12 minutes until golden brown. Remove from the oven, place on a rack and let cool off.
In the meantime, whisk the cream with the whisks of the hand mixer until stiff. Allow the vanillin sugar to trickle in. Spread the puff pastry without sugar evenly with plum puree and dust with cinnamon. Spread cream evenly on top. Place the puff pastry slices with sugar crystals as a lid on top. Serve immediately
40 minutes waiting time