Cut onions, leek and celery into strips. Sauté white onion and leek in butter, add clear soup, grate potatoes, carrot and celery into the pot.
Add the celeriac, stir and simmer for 20 minutes.
Mash the soup, add double cream and simmer for another 5 minutes on low heat. Season with nutmeg, pepper, salt and juice of one lemon.
Add the green onions with the shrimps and heat gently.