Clean the mushrooms and halve or quarter them depending on size. Clean, wash and slice the leek. Drain the pearl onions. Slice beetroot into thin slices. Mix vinegar, 2 tablespoons of water, salt, pepper and sugar.
Add 4 tablespoons of oil drop by drop. Mix beetroot and vinaigrette and leave to stand. Cook the pasta in plenty of boiling salted water for 10-12 minutes. Drain, quench and allow to drain.
In the meantime, heat 1 tablespoon of oil in a coated pan. Fry the meat for about 3 minutes. Add mushrooms and leek and fry for 2 minutes. Add pearl onions. Deglaze with wine and boil down briefly.
Add stock, bring to the boil and remove from the heat. Mix sour cream and binding agent and stir into the sauce. Wash, quarter and seed the tomato. Cut the flesh into cubes. Arrange noodles and ragout on plates.
Sprinkle with tomato cubes. Serve with beetroot salad. Garnish with oregano as desired.