- 1kg floury potatoes, such as maris piper or desirée, chopped
- 2 tbsp crème fraîche
- 1 tbsp Dijon mustard, plus 1 tsp extra for the sauce
- 500ml full-fat milk
- 125g butter
- 75g plain flour
- 2 fresh bay leaves
- Small bunch fresh dill, chopped
- 600g firm, skinless white fish, such as sustainable cod or pollock (or you could use salmon), cut into chunks
- 175g sustainable, undyed smoked haddock, skinned and cut into chunks
- 150g large, raw prawns, peeled
- 4 medium free-range eggs, boiled for 7 minutes (optional)
- 75g mature Cheddar, grated
- Cook the potatoes in a pan of boiling salted water for 12 minutes until tender, then drain well. Add the crème fraîche, 1 tbsp mustard, 50ml of the milk and 55g of the butter. Season well and mash until smooth.
- Meanwhile, to make the sauce, melt half the remaining butter in a medium saucepan over a medium- low heat. Add the flour, stir until it forms a smooth paste, then cook, stirring constantly, for 2 minutes. Off the heat, add a little of the milk and beat until smooth, then, over a low heat, gradually add the remaining milk, stirring, until smooth. Add the bay leaves and simmer for 5 minutes, then remove from the heat, season well and stir in 1 tsp mustard and the dill. (don’t worry if the sauce is thick, the seafood will add juice to the sauce while cooking to give it the perfect consistency.) Cool slightly.
- Preheat the oven to 200°c/ fan180°c/gas 6. Place the fish and prawns in a 1.5-litre ovenproof dish, pour over the sauce and mix well. Add the eggs (if using), spoon over the mashed potato, scatter with the grated cheese and dot the surface with the rest of the butter.
- Bake the pie for 30-35 minutes or until it is bubbling underneath and golden brown on top. Divide among plates and serve with buttered peas.
- Wrap the assembled, uncooked pie in cling film and foil and freeze for up to 2 months. Cook from frozen, adding an extra 20-30 minutes to the cooking time or until piping hot.