Fry the chopped spring onions lightly in a little butter and a small drop of vegetable oil over a low heat until they are cooked but not coloured.
Put the haddock or salmon in a pan with the bay leaf and the milk and bring it to the boil. Remove from the heat immediately and leave to stand – the fish will cook in the heat of the milk.
Boil the potatoes and sweet potatoes until they are soft, then mash them with a little of the milk from the fish, add a little butter, salt and plenty of pepper.
Mix the onions, mashed potatoes and parsley in a bowl.
Tear the fish into small pieces and gently mix them into the potato mixture (try to keep some pieces intact). Check the seasoning and add some salt and pepper if needed.
Shape the mixture into small balls and press them flat on both sides to make about 8 fish cakes.
Dip each one in flour, then in beaten egg, and cover with breadcrumbs, then lightly fry the fish cakes in a little oil until golden.