This dish is usually served as an hors-d’œuvre.
Soak the herrings in milk for about 1 hour. Put the wine and vinegar in a saucepan with the fish and, if necessary, add a little water. Add the sliced onion, the chopped garlic, herbs and a few peppercorns. Bring to the boil and simmer till the herrings are tender—this will not take more than a few minutes. Remove from the stock and, when cold, cover with a sauce made with a little of the stock, the sour cream, the yolks of egg, mustard, paprika and salt, all thoroughly mixed.