Peel and roughly chop onion, garlic, potatoes, and celery root.
Heat some olive oil in a pot, add vegetables to the pot and sauté vegetables. Deglaze with chicken broth, add cream and let simmer, covered, for approx. 15 min.
Chop salmon fillet. Season with salt, pepper, and lemon juice. Purée soup until smooth, add horseradish, and season with salt and pepper to taste.
Add salmon fillet to the soup and slightly heat until salmon is cooked through. Serve soup with a slice of bread and garnish with chives, more horseradish, and pumpkin seed oil.