Clean and gut the salmon or sea trout 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 litres. 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. Simmer for just 2 minutes and then turn off the heat. Keep the lid on and allow the fish to cool completely in the water (the fish should be just barely covered in the water).