Place the kippers onto a microwavable plate, add a tablespoon of water, cover with cling film and cook for 1 minute. Leave to cool and then flake into a bowl removing any bones. In a frying pan gently cook the leek in the butter until soft (about 5 minutes) and pop into the bowl with the flaked kippers then leave until cold.
Chop the black pudding into small pieces and add to the bowl along with the chopped parsley and the cold mashed potato. Mix well and season with a little salt and milled pepper. Divide the mixture into four and then form into cakes. Coat the cakes in the flour then dip into the egg and milk mixture and finally into the breadcrumbs.
Gently fry the cakes in the sunflower oil over a low-medium heat until golden brown and cooked through, this will take about 8-10 minutes.
Poach 4 eggs in simmering water with a touch of vinegar for about 3 minutes. Meanwhile warm the Hollandaise sauce and add the lemon juice. To serve, place the kipper cakes onto a plate, top with a poached egg and the hollandaise sauce.