Cut carps head in half , clean it from the eyes and gills. Wash it and cook in salted water until the head tenders.
Melt half spoon of butter in a pot and fry the veggies on it. Add cleaned carps insides cut into small pieces. Let simmer and then fill with the broth just so the veggies are sunk in it. Let cook for 15mins.
Make a roux from flour a the rest of butter and add it to rest of the broth. Thus stir it well and let cook for 15mins also.
Strain through the roux completing the veggie mixture, spice it with muscat, add meat we took of the carps head and let it cook for little longer.
Garnish the soup with chopped parsley, you can also used baked croutons.