To make the soup:
Peel and wash the celeriac. Cube it with a knife. Peel and finely cube the onion.
Heat 1 tbsp butter of butter in a saucepan and stew the onion cubes in it. Add the celeriac and briefly stew it, too. Add vegetable broth or water to the onion and celeriac mixture and leave it to simmer for 30 minutes.
Add the cream and blend the mixture until smooth, then add the remaining butter and season to taste with salt and pepper. Voilà, your celeriac cappuccino!
To make the raviolo:
To make the raviolo, use a round cutter (6 cm diameter) to cut circles out of the celeriac slices. Blanch the celeriac slices in a saucepan for two minutes (i.e., briefly pour boiling water over them). Plunge the slices into ice water and let them drip-dry on a piece of kitchen towel.
Peel, core and grate the apple. To make the filling, combine the grated apple, quark cheese and chopped chives and season to taste with salt and pepper.
Spread the filling on a slice of celeriac, place a second slice on top and press the sandwich together tightly.
Coat the raviolo in flour, egg and bread crumbs (regular or panko), then deep-fry it in hot seed oil.
To serve, ladle a spoonful of soup into a deep plate and place a raviolo in the soup.
