I made a batch of this today. This recipe has been in the family for generations. Relatives owned the fish-processing plant in Henningsvaer, Norway for approx. 100 years.
1.3 l Fish Stock
350 g (12 oz) cod (haddock works, too)
60 g (2 T) butter
1 onion, finely chopped (about 1/2 c)
1 large carrot, finely chopped
1 large leek (white and green parts) finely chopped
2 tsp sugar
2 T white wine vinegar
300 ml (1/2 pt) sour cream + whole milk or cream (2/3 sour cream, thinned with whole milk or cream)
chopped fresh parsley or dill to garnish
1. Bring stock to a boil.
2. Add the cod (I used a steamer pan with the fish submerged in the stock to m make lifting it out easier).
3. Heat to boiling and then pull off heat. Let cool until tepid.
4. Remove cod.
5. Melt butter in a large pan. Add veggies. Stir to coat. Cover pan, reduce heat, and let sweat about 20 minutes.
6. Add stock, sugar, vinegar, S&P.
7. Bring to boil, simmer for 10 minutes.
8. Stir in sour cream.
9. Stir in flaked cod. Adjust seasonings. Don't let it come back to a boil, but reheat it if necessary.
Serve garnished with chunks of cod, parsley/dill, carrot slivers.