Add all the stock ingredients to a pan and let simmer for 20 minutes.
Strain, reserving the fish meat, carrots, onions and garlic but discarding everything else.
Crumble the reserved fish into small pieces. Divide into portions of about 50 grams per person, and keep separate.
Add the remaining soup ingredients (butter, milk and sour cream) and simmer for 20 minutes. If you feel the soup is too thin, you can thicken with cornflour but this is usually not necessary.
When the broth is suitably thick, add the reserved carrots, onions and garlic.
To serve, divide the broth between the bowls, add a portion of crumbled klippfisk to each bowl and decorate with a sprig of rosemary.
Serve with bread.