If you are using whole fish, gut them carefully, scale if necessary and wash and dry well with kitchen paper. Cut 3 or 4 deep slashes diagonally on each side, almost to the bone. Put the fish on a tray and sprinkle it on both sides with coarse sea salt. Leave in the fridge for 2–3 hours, turning occasionally.
If you are using fish fillets there is no need to slash them, but salt them an