6-8 ounces of white fish (cod, haddock, etc.) 3-4 ounces of cooked and peeled prawns (optional) 3 medium-sized potatoes suitable for mashing One teaspoon of salt One and a half ounces of butter Half a pint plus two tablespoons milk Freshly-ground black pepper One heaped tablespoon of cornflour Teaspoon of English Mustard (optional) Sprinkle paprika (optional) Half an ounce of grated cheese (optional)