Prepare the mushrooms and the sauté. Boil the mushrooms in salted boiling water for 20 minutes. Meanwhile, heat 2 tablespoons of oil in a frying pan, add the onion and fry until golden. When the mushrooms are ready, add them to the frying pan with the onion, add the carrots and tomatoes, and simmer for another 5 minutes. Place the fried vegetables on a plate.
Prepare the cabbage. Add 1 tbsp of oil to the pan where the vegetables were fried and put the shredded cabbage. Fry over medium heat for 15 minutes.
Prepare the soup. Boil the water from the mushrooms. Add the fried mixture and salt. After boiling, add the chopped potatoes. Cook for 20 minutes. Put the cabbage in the pan and cook for another 10 minutes over medium heat.