Herring with Mustard Sauce

Sometimes in the ninth century, or perhaps earlier, Baltic fishermen figured out that curing herring in salt would preserve it. Caught and immediately salted to prevent spoilage, the fish was then brought back to French ports to be sold, often by Jewish purveyors who transported it up the Rhône. Salting fish was so important in the medieval period that salt-fish mongers, like fresh-fish mongers, had their own stores for salted, dried, and brined fish such as herring and cod. Because the fish had not in fact been cooked, rabbis considered salted fish to be kosher even if it had been salted by gentiles. For centuries Jews in northern France, who couldn’t eat pork, ate herring as their daily protein. It was prepared in a variety of ways, most often first soaked in milk to remove the excess saltiness, then dressed with vinegar and oil, and served with lots of sliced raw onion and hot boiled potatoes. Jews in France have put a French touch on their herring dishes, serving them as an appetizer rather than as a main course. They usually prepare the herring with either a horseradish sauce with apples, hard-boiled eggs, and beets, or a mustard-dill sauce with sugar, cream, and vinegar. To break the fast of Yom Kippur, Alsatian Jews use a sweet-and-sour cream sauce with their herring.