Clean and wash the kohlrabi and put the smaller leaves aside. Dice the kohlrabi and cut the leaves into fine strips. Peel and finely dice the shallot. Heat the fat in a pot and fry the shallot in it until transparent. Add kohlrabi and half of the leaves, steam briefly and deglaze with stock. Bring to the boil, cover and simmer for about 20 minutes.
In the meantime cut salmon into fine strips. Whip 100 g cream until semi-stiff. Add the rest of the cream to the kohlrabi. Finely puree the vegetables with a chopping stick. Season soup with salt and pepper and divide it into 4 soup bowls. Stir a dollop of cream into the soup and serve sprinkled with salmon strips and the remaining cut leaves.