Clean and gut the salmon carefully; do not remove the head, tail or scales. Carefully measure the water and half fill the fish kettle, adding 1 rounded tablespoon of salt to every 1.1 litre. Cover the fish kettle and bring the water to the boil. Add the salmon or sea trout and allow the water to come back to the boil. Cover and simmer gently for 20 minutes. Then turn off the heat and leave the salmon in the water until you wish to serve. It will keep hot for 20–30 minutes.