Grate the onion large on a grater. Peel the carrots and potatoes and grate them into very thin strips. Wash the rice.
In a saucepan melt the butter and sauté onion, potatoes and carrots. Season with salt and pepper. Add the rice, boiling water and simmer until half ready. Add the pieces of salmon, chopped and boil until all ingredients are boiled.
In a separate container mix the essential oil of anise in olive oil, add the lemon juice and mustard. Mix the ingredients well. Season the soup with ready mix or serve in a separate sauce-boat.
Garnish each bowl of soup with sour cream or strained yogurt.