Chop the onion and carrot finely and put them in about 8 1/3 cups (2 liters) of water in a pot on the stove. Add a little salt and pepper to taste.
Once lightly boiled, add the diced red pepper and allow to soften. Separately, fry 1 tablespoon of flour and add the sliced mushrooms with the chopped celery.
Fry everything nicely and gradually stir in the roux to the soup. Simmer until the mushrooms are ready and if desired, add 1-2 tablespoons of rice or vermicelli.
Finally, beat the sour cream, add a few spoonfuls of mushroom soup to it and temper it. Pour it in the soup and add salt and black pepper to taste.
Optionally, you can add chopped fresh dill or parsley.