Warm 200 ml whole milk until lukewarm, not hot.

Combine active dry yeast, 1 tablespoon granulated sugar, and the warm milk in a flour well.

Rest the yeast mixture in a warm place for 15 minutes until foamy.

Melt 130 g unsalted butter, then let it cool until lukewarm.

Add melted butter, the remaining sugar, and egg to the flour mixture.

Mix the dough until smooth and compact, adding a little flour only if necessary.

Cover the dough and let it rise in a warm place for 60 minutes.

Divide the risen dough into 6 equal portions.

Roll each portion into a small disc.

Place about 1 tablespoon plum jam in the center of each dough disc.

Seal each dough disc tightly around the filling and shape it into a ball.

Cover the dumplings and let them rise for 20 minutes.

Reserve a little of the 350 ml milk, then whisk it with sugar and egg yolks.

Whisk cornstarch and vanilla extract into the reserved milk mixture.

Bring the remaining milk to a boil.

Whisk the egg-yolk mixture into the boiling milk and cook until lightly thickened.

Pour about 1 litre water into the large pot and bring it to a simmer.

Place the dumplings in the steamer basket above the simmering water.

Cover tightly and steam the dumplings for 15 to 20 minutes without lifting the lid.

Pour vanilla sauce over each steamed dumpling.

Sprinkle each serving with poppy seeds and powdered sugar.