Peel and chop the onion. Peel potatoes, wash thoroughly and cut into cubes. Celery clean, wash and also dice. Heat 1 tablespoon of oil in a saucepan, fry the onion until transparent, add the potatoes and celery, fry briefly and deglaze with broth.
Bring to the boil, cover and cook over medium heat for about 20 minutes. In the meantime cut bread into small lozenges. Heat remaining oil in a coated pan, add bread and fry over low heat while turning.
In the meantime wash parsley, dab dry and chop finely. Sprinkle half of the parsley over the bread wedges. Take 1 tablespoon of celery cubes out of the soup and set aside. Puree the rest of the vegetables in the broth with a blender.
Season to taste with salt and pepper. Serve the soup with a dash of crème légere, sprinkled with coutons, diced celery and the remaining parsley. Garnish with parsley as desired.