Clean, wash and coarsely chop the soup greens. Peel onion. Place meat, bones, soup vegetables, onion, bay leaf, peppercorns, 1 tablespoon salt and 2 litres of water in a pot.
Bring to the boil and skim off the foam. Let it boil at medium heat for about 2 hours. For the dough knead flour, eggs, oil, 3-4 tablespoons of cold water and 1/4 teaspoon of salt to a smooth dough.
Form into a ball and let it rest for about 30 minutes. Wash and chop the spinach and herbs. Put 3/4 of the parsley aside. Knead herbs, spinach, egg, minced meat and breadcrumbs. Season with salt, pepper and nutmeg.
Roll out the dough thinly on a floured work surface. Use a dough wheel to roll out lozenges of about 5 cm in size. Put minced meat on half of the lozenges. Brush the edges of the dough with water. Place the remaining lozenges on top and press the edges of the dough well together.
Pour broth through a sieve and season to taste. Cook the Maultaschen in portions in the stock for 10-12 minutes and keep warm. Peel and finely chop the onions. Steam them in hot fat until golden brown.
Serve Maultaschen in the meat stock. Sprinkle with remaining parsley and onions.