Start by boiling the chicken in water, for about 20 minutes. Skim the soup as many times as necessary.
Meanwhile sauté vegetables (carrots, celery root, pepper and squash only), add garlic and continue to saute until the garlic is fragrant, about 1 minute.
Then transfer to the pot, together with chopped onion. Season with salt, pepper and bay leaves.
Boil for extra 10 minutes then remove chicken. When cool enough to touch, remove the meat from the bones as you will add the meat to the pot (optional).
Meanwhile, beat the eggs then add lemon juice, sour cream and flour.
Wash the rice a few times until the water is clear then add to the pot together with the chicken meat. Add 2-3 cups of water to the pot and continue boiling the soup for 15 more minutes.
Meanwhile temper the egg sauce: with a ladle, slowly pour some of the hot soup into the egg mixture, mixing vigorously with a whisk or fork. You should get a creamy sauce, the eggs should not scramble if you pour the soup slow and mix well while pouring.
Slowly pour the tempered sauce into the soup pot, mixing vigorously with a whisk.
Chop fresh dill and parsley and add some to the soup, keeping the rest for when serving the soup in bowls.