Clean and bone the herrings and put into a brine made from the salt and water. Leave for 2 hours, then drain. Cut the onions into thin rings and roll up the herrings, skin side outwards, with a few onion rings inside each. Pack herrings into a wide-necked jar together with chillis and bay leaves, and pour over the spiced vinegar. Seal and leave for at least 5–6 days before using.
Smoking is usually carried out commercially, following the time-old tradition of smoking over a fire, but these days it is usually a wood, rather than peat, fire. It is rather complicated and difficult to do at home, but if you are lucky enough to have a big catch you may find it worth while trying. The fish should first be cleaned and then, depending on the fish, they are either left whole (trout, buckling, smokies) or split (kippers, smoked haddock) or in the case of salmon they are usually boned. The fish are then put into a dry pickle for several days, before being hung up and smoked over a fire of peat or wood chips for 2–3 days.