Peel the onion, chop it into small cubes and let it translate in olive oil.
Wash, peel and cut the potatoes and celery tuber into larger pieces. Add to the onion cubes, roast well, extinguish with white wine and add approx. 1 1/4 l water. Salt, pepper and let everything cook until soft.
Puree the soup with a hand blender. Add the cream and nutmeg and mix everything well again with the hand blender.