Mix 300 g flour, eggs, 1 teaspoon salt, nutmeg and mineral water to a smooth, thick dough. Let dough rest for about 1 hour
Grate cheese. Bring plenty of salt water and oil to the boil. Little by little, put a part of the spaetzle dough on the moistened "spaetzle board" and scrape fine strips into the boiling salt water with a long pallet. Bring to the boil until the spaetzle rise. Lift out the spaetzle with a skimmer and rinse briefly in a sieve under cold water. Drain and keep warm. Process the remaining dough in the same way
Mix the spaetzle and cheese and place in a greased casserole dish. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 10-15 minutes. Peel onions, cut them into thin rings and turn them in 1 tbsp. flour. Tap off excess flour. Heat butter in a pan. Fry the onions until golden brown. Wash and roughly chop the parsley. Remove the spaetzle from the oven and spread onion rings on top. Sprinkle with parsley
Waiting time approx. 1 hour