Pickled Herring (Scandinavian Style)

Steps

1. Rinse the salt herring fillets under cold water. Submerge them in a large bowl with 1 quart (1 liter) of cold water and refrigerate for 8 to 12 hours, changing the water twice with the rest of the 3 quarts (3 liters). Taste a small piece: it should be about as salty as smoked salmon, without stinging your tongue. If it's still too salty, give it 2 more hours in fresh water.
2. While the herring soaks, make the brine. In a saucepan, combine the 1 cup (250 ml) of water, the sugar, and the vinegar. Heat over medium, stirring, until the sugar has completely dissolved and the liquid is just steaming, without letting it boil: the vinegar would evaporate.
3. Off the heat, lightly crush the allspice and peppercorns under the flat of a knife and add them along with the mustard seeds and bay leaves. Let the brine cool completely, then refrigerate it for at least 1 hour: it must be cold when you pour it.
4. Drain the fillets and pat them dry with paper towels. Pull out any bones sticking out along the back and any bits of fin with tweezers. Cut them on the bias into 3/4 inch (2 cm) wide pieces.
5. Halve the red onion and slice it into 1/16 inch (2 mm) half-moons. Peel the carrot and slice it into rounds of the same thickness. Pick half the dill into small sprigs for the jar.
6. Scald a 1 quart (1 liter) glass jar and its lid with boiling water, then let them air-dry. Layer the onion, carrot, herring, and dill sprigs, ending with onion, without packing them down.
7. Pour in the cold brine with its spices and bay leaves until the herring is covered by at least 1/2 inch (1 cm). Close the jar and refrigerate for at least 2 days: the pieces turn from grayish pink to ivory white and firm up. They are at their best between day three and day five.
8. On serving day, scrub the new potatoes and put them in a pot of cold water with the coarse salt. Bring to a boil and simmer for 15 to 20 minutes, until a knife tip slides in with no resistance. Drain and toss them with the rest of the dill, chopped.
9. Snip the chives. Lift the herring out of the jar with a fork along with some onion and carrot, let it drain, and plate it with the warm potatoes, a spoonful of sour cream sprinkled with chives, and slices of rye bread.