Crumble the yeast into a small bowl. Stir in 1 tablespoon of sugar until the yeast becomes liquid. Put 250 g flour, 1 pinch of salt, grated lemon rind and egg into a large bowl. Melt 50 g butter.
Add milk and warm up lukewarm. Add to the flour mixture with the yeast and immediately knead to a smooth dough with the dough hooks of the hand mixer. Cover the dough and let it rise in a warm place for about 45 minutes.
Wash the plums, cut lengthwise and stone them. Add 1 sugar cube to each plum. Press the plums together again.
Heat approx. 2 1⁄2 l water, 1 tablespoon salt, 75 g sugar, cinnamon stick, lemon and orange peel in a large pot.
Knead the yeast dough again. If the dough is too soft, knead in a little more flour. Form into a roll on a floured work surface and divide into 12 pieces. Press each piece of dough flat. Place 1 plum on top of each and form the dough into a dumpling.
Cover the dumplings and let them simmer in the boiling spice stock for about 15 minutes.
Melt 100 g butter, add breadcrumbs and roast. Lift the dumplings out of the stock, drain well and roll in the hot crumbly butter. Dust with icing sugar and serve immediately. Vanilla sauce tastes good with it.