Smoked haddock and mackerel fish pie

Method

1. Heat the oven to 220°C/200°C fan/gas 7. Bring a large pan of water to the boil and add the potatoes. Cook for 15 minutes until tender, drain, then add 20g of the butter, season generously with salt and pepper and mash until smooth.

2. Meanwhile, in a large deep saucepan, melt the remaining 50g butter and cook the onion for 5 minutes until beginning to soften. Stir in the flour and cook gently for 2-3 minutes until it smells toasty. Add the milk a little at a time, stirring well to make a smooth sauce, then simmer for 2-3 minutes until thickened slightly. Remove from the heat and season generously.

3. Gently stir in the mackerel, haddock, prawns and peas, then pour into a medium (about 1.5 litre) baking dish. Cover with the mash and sprinkle the cheddar on top. Bake for 30 minutes until bubbling, then serve with seasonal greens.