Peel the parsley root, potatoes and onion and cut into cubes. Melt the butter in a pan and briefly sauté the vegetables. Pour in the soup, add a little salt and cook until soft. Add the cream and purée, bring to the boil again and season to taste with salt, pepper and nutmeg.
For the garnish, peel and core the apple and dice into small cubes. Coarsely chop the nuts, roast them in a pan (without fat), add the apple cubes, dust lightly with icing sugar and sauté briefly.