Warm the milk, crumble the yeast and dissolve in it. Put flour, sugar, salt and fat in flakes in a bowl. Add yeast milk and knead until smooth. Cover and leave to rise in a warm place for about 40 minutes.
Wash, halve and stone the plums. Chop the plums finely. Mix 4 tablespoons apple juice and pudding powder until smooth. Boil up the rest of the apple juice, sugar and 1/2 teaspoon cinnamon. Stir in pudding powder and bring to the boil again.
Put the plums in the hot pudding and let them cool down. Knead the dough again. Roll out to a rectangle (approx. 36 x 48 cm) on a little flour. Cut out 12 squares (approx. 12 x 12 cm).
Separate the egg. Mix the egg yolks and 2 tablespoons of milk. Place 1-2 tablespoons of stewed plums in the middle of each dough. Brush the edges with the egg white. Fold the dough pieces into triangles.
Press the edges lightly with a fork. Spread the dumplings with egg yolk. Place on a baking tray lined with baking paper and leave to rise for another 15 minutes. Bake in a preheated oven (electric: 200 °C/ gas: level 3) for 15-18 minutes.
Let it cool down. Dust with icing sugar and cinnamon. Whipped vanilla cream tastes good with it.