For the soup, peel and finely dice the onion. Cut the celery and potatoes into medium-sized cubes.
Heat the oil in a saucepan and sauté the onion well.
Add the celery and potato cubes and sauté briefly.
Pour in the vegetable stock and simmer for 10 minutes.
Cut the bread into cubes and add to the soup. Let everything continue to simmer until the vegetables are soft. Then add the parmesan and puree the soup. Add the cream and parsley, bring everything to the boil again. Season to taste with salt and pepper.
For the garnish, peel the apple, cut in half, quarter, remove the core and cut into small cubes.
Toast the toast and then cut it into small cubes.
Pour the soup into plates, place the apple and toast cubes on top and serve immediately.