Put the fillet in a saucepan with cold water, put on high heat and bring to a boil. Remove foam, reduce heat, salt and cook for 8 minutes. Remove from the broth, let cool slightly, cut into small pieces.
Wash the pods of peas or beans, boil in boiling salted water (2 minutes). Drain in a colander and rinse with cold water. Wash the mushrooms and boil in boiling water for 3 minutes, drain in a colander. Strain the mushroom broth, cut the mushrooms into slices.
Boil the mushroom broth, reduce the heat, add sour cream, chicken meat, pea or bean pods and mushrooms. Season with salt and pepper to taste. Mix and cook 5 min. Pour the yolk into the dish, mix and immediately remove from heat. Serve with mashed potatoes.