1 Heat the oven to 180C/Gas Mark 4.
Ensure the potato mash is dry and still warm.
2 Place the fish on a baking tray and season with salt and pepper.
Put in the oven until just cooked, moving it around if necessary.
3 Once ready, add the fish to a large mixing bowl with the lemon juice and mashed potato and gently combine.
Then add the zest of lemon, capers, parsley, chives, spring onions and seasoning. Combine, being careful not to over mix.
4 Divide the mixture into 4 and form into fishcakes. Place them on a sheet of greaseproof paper and put in the fridge until fully chilled.
5 Season the flour and lay out the egg wash and breadcrumbs in small bowls.
Coat each fishcake in flour, then egg wash, then breadcrumbs.
6 Heat a deep fryer to 160C and cook the fishcakes for 5 to 7 minutes until golden brown all over, turning carefully if necessary.
Then place them in the oven for a further 10 to 15 minutes until the centre of each fishcake is piping hot.
7 Bring a pot of water to just below the boil and add a splash of vinegar. Crack the eggs into the water and poach for 3 to 4 minutes.
8 Heat the knob of butter in a pan and wilt the spinach. Season with salt and pepper. This should only take 2 to 3 minutes.
9 To serve, arrange the spinach on warmed plates, placing the piping hot fishcake on top with the egg on top of that.
Drizzle with a little olive oil, and finish with a grind of salt and pepper.