Smoked haddock and watercress fishcakes

Method

1. Put 75g of the butter into a small, shallow pan and leave over a low heat until it has melted. Leave it to settle for 1-2 minutes, then carefully skim any scum from the surface with a spoon, and pour the clear (clarified) butter into a small bowl, leaving behind the milky white solids which will have settled to the bottom of the pan. Set aside.
2. Peel the potatoes, cut into large chunks and put into a pan of salted water. Bring to the boil and cook for 20 minutes until tender.
3. Meanwhile, bring another wide, shallow pan of water to the boil, add the smoked and unsmoked haddock, and simmer for 8 minutes. Lift the fish onto a plate, and when cool enough to handle, break into flakes, discarding the skin and any bones.
4. Drain the potatoes and mash until smooth. Leave to cool slightly.
5. Melt the remaining butter in a large pan over a medium-high heat. Add the trimmed watercress and stir for 30 seconds until wilted. Add to the mashed potatoes with the flaked fish. Season and gently mix, trying not to break up the pieces of fish too much. Leave to cool.
6. Shape into 8 fishcakes measuring about 8cm across and 2.5cm deep. (Either use lightly floured hands or press the mixture lightly into an 8cm plain pastry cutter or cooking ring.) Chill on a cling film-lined tray for 30 minutes or up to 1 hour.
7. Preheat the oven to 200°C/fan180°C/gas 6. Heat half the clarified butter and 1 tbsp of the oil in a large non-stick frying pan over a medium-high heat. Add 4 of the fishcakes and fry for 2-3 minutes on each side until golden, turning them carefully. Repeat, adding the remaining clarified butter and oil, then bake on a lined baking tray for 5-10 minutes until heated through.
8. Serve the fishcakes with the watercress mayonnaise.