Warm up the milk. Put flour in a bowl, make a depression in the middle and crumble the yeast into it. Add 1 tablespoon of sugar and 100 ml of lukewarm milk and mix with some flour to a pre-dough. Cover and leave to rise in a warm place for about 15 minutes. Meanwhile melt 50 g butter, let it cool down and mix with the remaining milk. Add the egg, 1/2 teaspoon salt, 1 tablespoon sugar and lemon zest to the pre-dough and knead everything into a smooth yeast dough.
Cover and leave to rise for about 30 minutes. Knead the dough again, form it into a roll and cut it into 8 equal pieces. Press each piece flat and put 1 teaspoon of plum jam in the middle of each. Press the dough together and form into dumplings. Place on a floured baking tray, preheat oven to approx. 50 °C, turn off. Let dumplings rise in the warm oven for another 20 minutes. Bring approx. 150 ml salt water to the boil. Place 3 dumplings side by side in a perforated insert (e.g. of the pressure cooker or a fish pot) and cook covered over a low to medium heat for about 20 minutes. Remove the finished dumplings and prick them a few times with a wooden skewer. Place the dumplings on a greased baking tray and keep warm. Prepare the remaining dumplings in the same way.
Bring approx. 150 ml salt water to the boil. Place 3 dumplings side by side in a perforated insert (e.g. of the pressure cooker or a fish pot) and cook covered over a low to medium heat for about 20 minutes. Remove the finished dumplings and prick them a few times with a wooden skewer. Place the dumplings on a greased baking tray and keep warm. Prepare the remaining dumplings in the same way. Mix poppy seeds and remaining sugar and sprinkle on the dumplings. Melt the remaining butter and pour over the dumplings
Serve with vanilla sauce