For the cakes: Peel and wash the potatoes and cut them into pieces. Cook in salted water for about 20 minutes. In the meantime wash the fish. Covered with lemon juice and wine, steam over medium heat for about 10 minutes. Lift out the fish and collect the stock. Drain potatoes and mash finely.
Wash herbs. Chop the parsley, cut the chives into small rolls. Knead fish, potatoes, parsley and half of the chives. Season to taste with salt and pepper. Leave to cool. Form 8 cakes from the lukewarm mixture with floured hands. Cover them and put them in a cool place for about 1 hour.
For the sauce: Boil down the fish stock and 3 tablespoons of water in a small pot to about 2 tablespoons. Stir in double cream. Gradually stir in butter in small pieces with a whisk to create a smooth, shiny sauce. Add the rest of the chives. Season the sauce with salt and pepper.
For the cakes: Heat the oil in a large pan. Fry the cakes on each side at medium heat for about 5 minutes. Serve with the sauce. Serve with a mixed salad.