Peel the potatoes, chop into even-sized chunks and cook in a large pan of boiling salted water for 15 minutes, or until tender.
Meanwhile, peel and finely chop the onion, place in a medium pan on a medium-low heat with 1 tablespoon of olive oil and cook for 10 minutes, or until softened, stirring regularly.
Stir in the flour, gradually stir in the milk, and keep stirring until thickened.
Gently poach the smoked haddock in the sauce for 5 minutes, making sure it’s covered, then scoop out the fish and put aside, removing any skin.
Finely chop the chives, then put one quarter into a blender, pour in the sauce and blitz until silky smooth (in batches, if needed).
Return to the pan and simmer on a low heat to the consistency of your liking.
Drain the potatoes and mash well, then beat and mix in the egg, with most of the remaining chives and a small pinch of sea salt and black pepper.
Flake in the poached haddock, mix well, then divide into eight and shape into patties.
Fry the fishcakes in 1 tablespoon of oil in a 30cm non-stick frying pan on a medium heat for 5 minutes on each side, or until nicely golden and cooked through.
Season the sauce to perfection and divide between your plates, then sit the fishcakes on top.
Sprinkle with the remaining chives, drizzle with ½ a tablespoon of extra virgin olive oil and serve with lemon wedges, for squeezing over.
