How to make them:
Mix the softened butter with the vanilla sugar and a small pinch of salt until creamed through. Stir in the egg with the quark and flour and work into a malleable dough. Form into a ball, wrap in film, and leave in a cool place to rest for approx. 30 minutes.
Remove the stones from the plums and place a sugar cube in their place.
On a floured work surface shape the dough into a roll of approx. 5 cm / 2 in thickness. Cut off slices and gently press these flat between the hands. Place the plum into the dough, press the dough around it, and seal well. Apply some flour to the hands, form dumplings, and place on a floured board.
Bring a generous amount of slightly-salted water to a boil in a large saucepan. Turn down the heat, place the plum dumplings in the water, and allow to simmer gently for 10 – 13 minutes. Stir carefully from time to time to prevent the dumplings from sticking to one another.
For the garnish, melt the butter in a pan. Add the breadcrumbs, flavour with cinnamon, and fry until golden yellow in colour. Towards the end, add a generous quantity of sugar. Carefully remove the cooked dumplings and roll in the prepared sugared breadcrumbs. Arrange and dust with icing sugar.
To ensure that the dumplings do not fall apart, it is advisable to make a test dumpling before filling with the fruit. If necessary, adjust the dough mix by adding more flour if too soft, or by adding butter if too firm.