Mix flour, eggs, a pinch of salt and water to a spaetzle dough. Beat well until bubbles appear. Leave the not too liquid dough to rest for half an hour so that the flour can swell.
In the meantime, fry the onion rings in butter in a pan.
Bring slightly salted water to the boil and scrape the spaetzle dough from the wooden board into the boiling water with a knife (it's easier with the spaetzle slicer!)
As soon as the spaetzle rise, take them out with a skimmer and let them drip off. In a preheated bowl, alternately fill a layer of spaetzle and grated Allgäuer Emmental cheese. Finally fill in a layer of spaetzle and sprinkle with the roasted onions.