Warm the milk lukewarm. Crumble yeast into it and dissolve while stirring. Put 500 g flour in a bowl. Press a depression in the middle. Add yeast milk and 1 tbsp. sugar, mix with some flour from the rim to the pre-dough.
Cover and leave to rise in a warm place for about 15 minutes.
Melt 50 g butter, let it cool down a little. Add the egg, 1 pinch of salt and 1 tablespoon of sugar to the pre-dough. Knead with the dough hooks of the mixer to a smooth yeast dough. Cover and leave to rise in a warm place for about 30 minutes.
Knead dough briefly. Divide into 6 equally sized pieces. Press each piece a little flat. Put 1 tbsp. plum jam in the middle of each piece. Press the dough over it and form into dumplings. Place on a floured baking tray with the seam facing down.
Cover and leave to rise for about 20 minutes.
Bring approx. 150 ml of water to the boil in a pot with a steam insert. Place about 2 dumplings next to each other in the steamer basket. Cover and steam for about 20 minutes at low heat. Prick the finished dumplings with a skewer so that the steam escapes and take them out and keep them warm until they are cooked.
Heat 80 g butter, add poppy seeds and roast for about 1 minute while stirring. Arrange dumplings on plates. Pour over poppy seed butter and dust with icing sugar. Vanilla sauce is also delicious with it.