Method:
Preheat the oven to 180 fan.
To make the topping
- Cut the potatoes into large chunks and boil in salted water until tender β around 20-25 minutes.
- Drain well and mash with a knob of butter and a splash of milk until smooth.
- Season with salt and pepper.
To make the filling
- Melt the butter in a large saucepan then stir in the flour.
- Cook on a low heat for 2 minutes to make a roux.
- Add the spring onions and cook for another minute.
- Add the milk gradually, whisking with a balloon whisk until smooth. Cook for 4-5 minutes until thickened.
- Remove from the heat and gently stir in the trout, smoked haddock, mustard and season well with salt and pepper.
- Pour into an ovenproof dish and spoon over the mashed potato topping.
- Sprinkle over grated cheese if using.
- You can freeze it at this point if wished. Once the dish is completely cold wrap in double layers of cling film and pop in the freezer.Β Defrost before cooking.
- Cook in the oven for 25 minutes until golden and bubbling at the sides.
- Serve with peas or broccoli.