We are on GAPs, and here's the fermented fish recipe:
For a one-litre jar you need 3-4 fresh herrings or mackerel. Skin the fish and remove the bones, cut into mouth size pieces. Put the pieces of the fish into the jar mixing with peppercorns, a few slices of white onion (optional), coriander seeds, bay leaves and dill seeds or dill herb. In a separate jug in 1/2 litre of water dissolve 1 tablespoon of sea salt and 3-4 tablespoons of whey. Pour this brine into the jar with the fish until the fish is completely covered; if the fish is not covered just add more water. Close the jar tightly and leave to ferment for 3-5 days at a room temperature, then store in the fridge.
Buy some fresh sardines (also works for herring and mackerel), de-scale the fish, cut the heads off and clean the belly out. Put into a suitable size glass jar or a stainless steel pan. Add 1-2 cups of whey, 1-2 tablespoons of salt (per 1 litre), a teaspoon of black pepper corns (freshly crushed), 10 bay leaves and ½ a teaspoon of coriander seeds (freshly crushed). Top up with water so the fish is completely covered with water, you may want to float a small plate on top of the fish to keep it submerged in the brine. Cover the pan or put the lead on the jar and let it ferment for 3-5 days at a room temperature. When the fish is ready take the meat off the bones, cut into bite-size pieces and serve with fresh dill and some chopped red onion.