For the caramelized grapes, preheat the oven to 180 °C (350 °F) conventional oven (top and bottom heat).
Wash the 100 g grapes and pull them off the stems.
Place the individual grapes in a small baking dish with 1 pinch salt and drizzle with 1 tbsp liquid honey.
Finely chop the needles of 2 sprigs rosemary and sprinkle over the grapes.
Peel and clean 1 kg celery root (celeriac) and 200 g potatoes, cut into rough pieces and set aside separately.
Also peel 1 onion and 1 clove garlic and cut into small cubes.
Put the baking dish with the rosemary grapes in the oven and let them caramelize for approx. 25 - 30 min.
Heat 1 tbsp butter in a large pot.
Sauté the prepared celery root, onions and garlic in the pot for approx. 5 min., stirring.
Then add the potato pieces and pour in 1 l water.
Add 1 tsp salt, bring to a boil and simmer gently with the lid on for approx. 20 min.
In the meantime, finely chop the leaves of 0.5 bunch parsley and the 50 g walnuts.
Remove the crusts from the 3 slices sandwich bread and carefully split each slice horizontally into two thin slices.
Cut the thin slices into even cubes.
Heat 1.5 tbsp butter in a small pan and toast the little bread cubes for approx. 4 minutes until crispy, turning them.
Add the nuts and toast briefly with them.
Season with salt and pepper, stir in the finely chopped parsley and set aside.
Finely grate the 100 g Parmesan and have it ready.
When the soup has finished simmering, remove from the heat and carefully purée until smooth with an immersion blender.
Bring to a boil once more, add the grated Parmesan to the soup while stirring and let it melt.
Stir in 3 tbsp crème fraîche to taste and simmer for another 2 minutes.
Season the finished soup with salt, pepper and nutmeg.
To serve, garnish the soup with 1 - 2 tbsp caramelized rosemary grapes and the walnut-parsley croutons.