Thoroughly wash the livers under running water and then put them to boil in water on the stove. Drain them and thrown out the water.
Put 4 1/5 cups (1 liter) of water with the livers in a clean pot. Peel the potato and put it whole in the pot. Add the cleaned and finely chopped carrot and onion. Once boiling, add the salt, tomatoes, a little oil and stir with a wooden spoon. Reduce the heat and simmer for about 30-35 minutes.
Then remove the potato, puree it and put it back in the soup. Add the vermicelli and boil for about 15-20 minutes. Turn off the heat and season with the tarragon and a little savory.
Once the soup has slightly cooled, thicken it carefully with the beaten yoghurt, eggs and 1 tablespoon of vinegar.