Preparation:
Cut the fish into large pieces, about 100g each. Wash the cockles well. Place the smoked fish in a saucepan with the milk for the sauce and season lightly with salt and pepper. Cover with a ‘lid’ of parchment paper and bring to the boil, then remove from the heat and allow to cool. Drain off the milk and reserve for the sauce; flake the fish into a large bowl and set aside. Grate the cheese for the sauce. Blanch the peas in boiling salted water for 1 minute. Drain and blend to a very rough purée in a food processor. Finely slice the spring onion. Pick the leaves from the tarragon and chop them. Chop the dill tops. Make the mash with the ingredients above. Check the seasoning and set aside in a piping bag at room temperature until ready to use. Set up a steamer or, if you don’t have one, use a colander over a pan of boiling water and a lid that will almost fit.
Method:
Make the sauce. Melt the butter in a saucepan over a low heat, add the flour and stir well with a wooden spoon, then cook for 5 minutes without colouring the flour. Pour the milk from cooking the fish into a separate pan and bring to the boil, then add to the flour and butter a little at a time, stirring continuously until it has all been poured in. Now turn the heat down to the minimum setting and cook the sauce for 15 minutes, stirring regularly. Remove the pan from the heat and season the sauce with salt and pepper, then stir in the cheese, mustard, Worcestershire sauce and a good grating of nutmeg. Leave the sauce to cool slightly. Preheat the oven to 220°C/200°C fan/gas 7. Meanwhile, place the unsmoked fish in the steamer and steam with the lid on for 2 minutes. Remove and cool slightly, then flake into the bowl with the smoked fish. Check carefully for any bones, trying to keep the fish in the largest pieces possible. Spoon the peas into a 2 litre pie dish. Combine the fish with the sauce, spring onion and herbs, spoon into the dish to cover the peas and pipe the mash on top. For a crunchy topping and a fantastic finish, grate the cheese and sprinkle the breadcrumbs over the mash, then place the cockles on top and press them in gently. The cockles will open during baking and release their wonderful saltiness into the pie. Place the pie in the oven and bake for 20 minutes. Serve with a side dish of extra peas with a knob of butter and some mint.
Tip
A good ratio for the layers in the pie is 25 percent peas, 50 percent fish and 25 percent mash.