Wash and cut leeks into rings. Fry minced meat, stirring continuously. Add leeks and fry them some minutes, then add beef stock and season with salt, pepper and marjoram. Let the soup simmer about 15 minutes.
Cut cheese into small peaces and mix well with the soup until cheese has melted. Wash and quarter mushrooms. Fry them about 3 minutes and add parsley.
Serve cottage soup with mushrooms.