Line a cookery bowl with a thin layer of salt, add 1 lb. fresh herring fillet and cover with more salt, turning to make sure every surface is coated. (About 1/2 cup salt is needed for this recipe.) Cover and keep at room temperature for several hours or overnight.

Next day rinse fillets and dry on absorbent paper. In pot, combine 1 cup water, 6-8 peppercorns, 3 grains allspice, 1 bay leaf, 1/2 teaspoon mustard seeds and 1 teaspoon sugar. Bring to boil and simmer 3 minutes. Add 1 cup 6% vinegar and bring to boil. Switch off heat, cover, and let stand until cool.

Through sieve, dust herring fillets with flour and fry in several Tablespoons oil until golden on both sides. Transfer to casserole or glass or crockery bowl or container with tight fitting lid. In pan drippings, sauté 1 thinly sliced onion and 1 small thinly sliced carrot until tender, then pour over herring. Drench with cold marinade, cover and refrigerate, at least overnight before serving. They will be even tastier after longer marinating. 

Note: Fish fillets other than herring may be prepared the same way.