1 Pot, 1 Potato ricer, 1 Bowl, 1 Hand mixer, 1 Fine grater, 1 Citrus juicer, 2 Small bowls, 1 Teaspoon, 1 Small pot, 1 Small knife, 1 Cutting board, 1 Whisk, 1 Rolling pin, 1 Cutting board, 1 Pot, 1 Small skillet, 1 Tablespoon, 1 Ladle, 1 Slotted spoon, 1 Fork, 1 Pastry wheel
1 Scrub the potatoes and cook in boiling salted water until knife-tender, 20-25 minutes. Drain, rinse under cold water and peel, then press while still hot through a potato ricer into a large bowl (or crush finely with the potato masher). Allow to cool for about 10 minutes.
2 Meanwhile, rinse orange in hot water, wipe dry and gfinely rate 2 teaspoons zest into a cup. Cut the orange in half and squeeze about 100 ml juice.
3 Mix 2 tablespoons orange juice with the cornstarch in a small bowl.
4 Bring remaining orange juice, milk, 2 tablespoons sugar and orange zest to a boil in a small pot. Halve vanilla bean lengthwise, scrape out the seeds with a knife and add to the pot. Set aside to steep.
5 Rinse and dry the plums. (Note: Do not pit the plums; otherwise the fruit juices would cause the crust to become too soggy.)
6 Knead together egg, semolina and 150 grams (approximately 1/4 cup) of flour into the mashed potatoes with the dough hook of a hand mixer.
7 Roll out dough on a floured work surface to about 5 mm (approximately 1/4 inch) thick. Cut out 18 squares with a pastry cutter or knife, each about 10 x 10 cm (approximately 4 x 4 inches).
8 Place 1 plum onn each piece of dough. With floured hands, wrap dough around fruit and seal edges, being careful not to tear the dough. Set the dumplings on a floured board.
9 Fill a large pot with water and salt generously. Boil the water and slide in the dumplings so that they lie side by side. Reduce heat and let the dumplings simmer, covered, for 15-20 minutes; do not boil.
10 Meanwhile, mix together cinnamon and remaining sugar. Toast poppy seeds in a small dry pan until fragrant. Then add the butter and brown slightly.
11 Heat the orange sauce briefly and spread on the plates. Take the plum dumplings with a slotted spoon from the water and set on plates. Top each with 1 tablespoon poppy-seed butter. Serve sprinkled with cinnamon sugar.