Wash the potatoes, cook them for about 20 minutes, let them evaporate and peel them. Press through the potato press while it is still hot. Knead with the flour, egg, salt, sugar, vanilla sugar and lemon zest to form a smooth dough.
Bring salted water to a boil in a large saucepan. Shape the dough into finger-thick rolls on a floured work surface. Cut off small pieces and roll them with your hands into about 6 cm long, pointed noodles. Put the pasta in the boiling water and let it steep for about 8 minutes over low heat, lift out and drain well.
Melt the butter in a pan, fry the pasta in it until golden brown. Stir in the poppy seeds. Serve the poppy seed noodles sprinkled with powdered sugar.