Leave for at least 24 hrs but no longer than 48.
Drain and place in cold water only for at least 12 hrs to desalinate.
Dissolve 300gms sugar in 200ml water with 100ml vinegar wine. Add peppercorn, juniper berries, bay leaves, mustard seeds, cloves. Cool.
Mix 300 grams of dijon and wholegrain mustard with a generous bunch of chopped dill and add into the syrup.
Mix with herrings and marinate for 24hrs — will last for 3 weeks.
Recipe courtesy of Aidan Mac Manus, Chef Patron, King Sitric, Howth