Peel and roughly chop the onion. Peel, wash and chop the celeriac. Clean and wash the celery, put aside about 1/2 stick and some celery green for garnishing. Cut the rest of the celery into pieces.
Peel, wash and roughly dice the potatoes.
Heat 2 tablespoons of oil in a saucepan and sauté the onions until translucent. Add the potatoes, bay leaves and celery and fry, season with salt and pepper. Deglaze with stock and apple juice, bring to the boil, cover and cook for 18-20 minutes.
In the meantime, cut bread into about 8 slices, drizzle with 2 tablespoons of olive oil and place them next to each other on a baking tray. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 6-8 minutes.
In the meantime, mix cream cheese and gorgonzola. Season with pepper. Wash the prawns and pat dry. Clean and wash the chilli and cut into fine rings. Heat 2 tablespoons of oil in a large frying pan and fry the prawns for about 3 minutes, turning them over.
Add chilli, season with salt, pepper and paprika.
Cut the celery that has been set aside in the meantime very finely. Remove the soup from the stove, remove the bay leaves. Puree the soup finely, season to taste with salt, pepper and sugar. Spread slices of bread with cheese cream.
Arrange the soup in small bowls, sprinkle with prawns, celery green and finely chopped celery. Garnish with chilli peppers if desired. Add the crostini.