The local herring season in San Francisco arrives in December or January, and we fillet, salt, and pickle thousands of these tasty baitfish during their short season. We make a big bucket of fish sauce every year with the remnants of the herring that didn’t get pickled. If you choose to do so, we highly recommend that you go way out in the country away from neighbors. We cover the bones with solé and let it sit for a year at room temperature. Then we strain it and let it age for another 6 months. It can be used in just about anything; we like it in the green chili fish stew.
There are many variations of pickled herring, including one seasoned with curry, but this sour cream version is our favorite. We like it with dark bread and fresh dill.
Sardines or mackerel are good substitutes for herring. Salted herring, which is available from specialty food stores and some well-stocked supermarkets, can also be substituted for fresh herring. It has a higher salt content than the herring in this recipe, however, so soak it overnight in 4 cups/960 milliliters water or milk and go directly to making the brine, skipping the step of salting the fish overnight.
Arrange the herring fillets flesh side-up in a single snug layer in a small baking dish. Season the flesh side with 1 tablespoon of the salt. Cover the dish and refrigerate for 24 hours.
In a small nonreactive saucepan over low heat, combine the vinegar, brown sugar, garlic, peppercorns, mustard seeds, bay leaves, and remaining 1 tablespoon salt. Bring to a simmer and cook, stirring occasionally, to steep the aromatics and dissolve the sugar to create a brine, about 15 minutes. Strain the mixture through a fine mesh sieve into a nonreactive container. Add the onion to the brine, cover, and refrigerate until cold, about 2 hours.
If you have a butane kitchen torch, gently run the flame over the skin of the fillets to tenderize. If you don’t have one, the herring will still be good, but just a bit less tender on the skin side. Add the herring to the cold brine, cover, and refrigerate for 2 days.
Pour off the brine from the herring and onion and discard the bay leaves. Separate the onions and the herring, then cover and refrigerate the herring. Transfer the onion to a large nonreactive bowl, add the sour cream, and stir gently to mix well. Cover and refrigerate for at least 1 hour before serving. The pickled herring and the onion mixture can be stored in the refrigerator for up to 1 week.
Spoon pickled onion onto sliced rye bread and top with herring fillets. Garnish with dill and pepper. Serve immediately.