Soak the plums for at least 120 minutes covered with water. Drain well.
Cut off the plums. Finely grind them in a cutter with the sugar, the juice of one lemon and the kirsch.
Roll out the puff pastry thinly. Cut out roundels (number = 3 x number of pieces) with a diameter of eight cm. Place 1/3 of the rounds on a baking sheet lined with parchment paper.
Cut a six cm diameter hole in the center of the 2nd third of the rounds. Brush the resulting dough rings with a small amount of egg white and place them with this side down on the rondelles on the baking sheet.
Cut out a two-cm diameter hole in the remaining rondelles.
Place all the dough scraps from the cutting on top of each other and roll out exactly. Cut out another round (number = number of pieces) with a diameter of four cm. From these again cut out a hole of two cm in diameter. Brush the resulting dough rings with egg white and place them on top of the remaining rondelles, which now form the lid of the pastetli.
Fill each round on the baking sheet with 1 spoonful of plum puree. Brush the edges of the pastry with a little egg white and cover with the prepared lids.
Meanwhile, bake the plum pasties in the oven heated to 200 °C on the second rack from the bottom for twenty minutes. Cool.
Sprinkle with powdered sugar before serving.