Wash the potatoes thoroughly and cook in plenty of boiling water for about 20 minutes. In the meantime wash, clean and slice the tomatoes. Peel 2 onions and cut into rings.
For the vinaigrette, mix vinegar, salt, pepper and sugar, then fold in 3 tablespoons of oil. Place the tomatoes and onion rings in a bowl and fold in the vinaigrette. Peel the remaining onion and chop finely.
Clean and clean the mushrooms and cut them into slices. Wash the meat, dab dry. Drain potatoes, quench, drain and peel. Press warm potatoes through a potato press.
Add flour and eggs, knead briefly and season with salt, pepper and nutmeg. Form rolls (approx. 1.5 cm Ø) from the dough, cut into small pieces and form into balls with floured hands.
Press flat with a fork. Bring plenty of salted water to the boil in a large saucepan. Cook the gnocchi in lightly simmering salt water in 2-3 portions. Remove the finished gnocchi with a skimmer and drain well.
Keep the gnocchi warm. Season meat with salt and pepper. Heat 2 tablespoons of oil in a large frying pan. Fry the meat for about 5 minutes, turning it over, remove it and keep it warm. Sauté diced onions in hot frying fat until translucent.
Add the mushrooms and fry for about 4 minutes. Season with salt and pepper. Add 250 ml water, stir in sauce powder, bring to the boil and simmer for about 1 minute. Wash the parsley and chop it, except for something to garnish.
Arrange meat, mushroom sauce, gnocchi and tomato salad on plates. Sprinkle with parsley and garnish.