In a large bowl whisk flour with salt, 2 ½ tbsp (25g) sugar and lemon zest.

In a small bowl stir fresh yeast with 1 tsp (5g) sugar until it liquefies. Dissolve the yeast with milk and pour it over flour mixture. Add beaten egg, melted butter and vanilla extract and knead the dough until smooth, for about 5 minutes. Cover and let it rise at room temperature for about 1 hour or until doubled in size.

In a small bowl combine the plum jam with rum if used.

On a floured surface divide dough into 4 or 5 pieces. Flatten each piece of dough using your hands and fill each with about 1 tbsp of plum jam mixture. Seal well and form each piece into a ball. Place the dumplings into a floured surface, cover with a kitchen towel and let them rest for 30 minutes.

Meanwhile prepare the vanilla sauce. In a small saucepan whisk the egg yolks with sugar, cornstarch and vanilla extract. Gradually whisk in milk and cream and place over medium-low heat. Cook for about 6 minutes, stirring continuously until thickens. No need to boil the sauce. Set aside until ready to use.

In another small bowl combine the ground poppy seeds with powdered sugar to have them ready for serving.

In a pot bring water to a simmer, up to 1 inch (3 cm). Use a greased steamer basket and place it in the pot. Add the dumplings, cover the pot with a lid and let them steam for about 15-17 minutes.

Serve the dumplings immediately. Pour vanilla sauce and poppy seed mixture on top.