Prepare the marinade. Mix sugar, salt and crushed garlic. Add the juice of half a lemon.
Boil the mushrooms. Place the champignons in a saucepan and cover them with water, add salt and boil for about 10 minutes.
Prepare the mushrooms for marinating. Cut the champignons into slices, place them in a bowl and pour the marinade over them. Mix thoroughly and cover the bowl with a plate or cling film. Leave in a cool place for 8-12 hours.
Prepare the frying. Put the onion in a preheated frying pan and fry for 2-4 minutes, stirring occasionally. When the onion becomes transparent, pour in the carrots. Mix thoroughly and leave to fry over low heat. When the carrots release juice, become soft and lighten in color, the frying is ready.
Boil the rice until half-cooked. Take a saucepan and fill the rice with water in a ratio of 1:2. Cook over medium heat under a closed lid until half-cooked, this will take 10-12 minutes. Drain off excess liquid and cool the rice by placing it in a sieve.
Start cooking the soup. Add potatoes and rice to the pan, pour water over all the ingredients. Salt to taste, add peppercorns and a clove of garlic. Put on medium heat and bring to a boil. After boiling, the soup should be cooked for about 7 minutes.
Finish cooking. In a bowl, beat the egg with a pinch of salt using a fork or whisk. Then pour it into the soup in a thin stream, stirring with the other hand so that it is evenly distributed throughout the broth. Add the mushrooms and simmer the soup for about 10 more minutes. Add finely chopped spinach or any other greens. Turn off the heat and leave the soup to steep, covered, for 20 minutes.