Melt the butter. Fry finely chopped onions for about 5 minutes.
Cut the mushrooms into 4 parts, add to the onion and fry for another 5-7 minutes. Add potatoes.
Pour 2 tablespoons of flour, mix well. Pour in the broth slowly, stirring constantly so that there are no lumps. Salt the pepper. Cook for 15-20 minutes.
Pour into a blender and grind well until smooth. Return to the pan, pour the cream, bring to a boil.
Pour hot soup into plates, sprinkle with finely chopped parsley.