Preparation: About 15 min.
Cooking time: Total 12 min.
Should not be frozen
4 large herring or small mackerel
5 dl [1 pt] water
1 tablespoon vinegar
1 tablespoon salt
1 bay leaf
1-2 tablespoons butter
1-2 tablespoons unsweetened mustard
2 tablespoons flour
1 dl [0,2 pt] cream, 20 or 35%
 Remove the bones from the herring/mackerel, but let the fillets still be attached along the back. Roll the fillets together, separately.
 Cook a brine of water, vinegar, salt, bay leaves and peppercorns. Put the fish rolls in the brine and let them steep for about 8 min just below the boiling point. Keep them warm.
 Clean and chop the onion and fry it in butter until soft. Add the mustard and stir in the flour. Dilute with the cooking brine and let the sauce boil over low heat for 3-4 minutes. Add cream and taste with salt and freshly ground white pepper. Put the fish rolls in a hot serving dish and pour the sauce on top.
Serve immediately with boiled potatoes as an accessory.