Peel and chop the onion and garlic. Peel, wash and finely dice the potatoes. Clean, wash and dice the zucchini. Heat 1 tablespoon of oil in a saucepan, fry the onion and garlic while turning.
Add potatoes and zucchini and also fry briefly. Season with salt and pepper. Deglaze with broth, bring to the boil covered and cook over medium heat for about 15 minutes. In the meantime knead minced meat and egg yolk.
Season with 1 level teaspoon of salt and pepper. Form small balls from the mixture with moistened hands. Heat 2 tablespoons of oil in a pan. Fry the meatballs for about 5 minutes, turning them over.
Wash parsley, shake dry and cut into fine strips, except for a little to garnish. Remove the potato and courgette vegetables from the heat, remove 2 tablespoons of vegetables and set aside.
Puree the remaining vegetables in the stock with a blender. Season again with salt, pepper and nutmeg. Add meatballs. Sprinkle with zucchini and potato cubes and parsley. Garnish with parsley.