Heat milk and just before it starts to boil, turn down the heat, place in salmon and cod and simmer for 5 minutes.
Chop prawns, and after fish has been simmering in milk for 5-10 min, flake it into little pieces. Mix fish, prawns and potatoes together, adding salt and pepper (to your taste), and mayonnaise and/or sour cream.
Put beaten eggs in flat bowl. In another bowl place flour, and in a third bowl breadcrumbs (I once didn`t have breadcrumbs and I crushed breakfast cornflakes- was even better!!!! Since then I haven`t used breadcrumbs).
Make patties from mixture- in size of flat tennis ball. Dredge the patties first in flour, then egg and lastly in breadcrumbs.
In large pan heat (about 2mm) oil and cook each patty till golden brown. As it will not be hot inside and to prevent from burning, put cooked fish cakes on an oven tray and place in oven (200 C) for 8-15 minutes or until they are piping hot inside.