Sift the flour and salt into a bowl. Add eggs, stir in mineral water and make a smooth dough. Finally, let the poppy seeds trickle in. The dough is ready when it tears from the spoon, tough. In a large saucepan, bring the water to the boil with a pinch of salt. Place a bowl of cold water next to the stove. Scrape the dough in portions from the wooden board into the boiling water, it works better with the help of a spaetzle slicer. Let the spaetzle boil briefly. Remove with a slotted spoon and rinse in the bowl of cold water. Drain well over a sieve.
Heat the butter in a pan, toss the spaetzle in it and serve immediately