Thomasina says: “The seemingly endless car journeys of my childhood, gazing out of the window at the grey tarmac of motorways, or Welsh hillsides dotted with the occasional turreted castle, bickering with my siblings… If these are still strong in my memory, so, too, are the arrivals at our respective grandparents’ houses. Exclamations of joy, comments on appearances, large whiskies poured and the much-loved dishes we always had on those Friday nights, appearing magically from the depths of the Aga and filling the kitchen with the most delicious smells.

“At one grandmother’s, it was her leek quiche with buttery shortcrust pastry, plumped up with the molten leeks and golden cheese crust; at the other’s, sometimes a bobotie, a dish from her South African childhood, but more often than not her fish pie. In those days, the glimpse of a pink prawn was wonderfully exotic, although the dish itself, I fear, did not always live up to the memory of it, steeped as it was in the pleasure of arrival at that cosy home of tiddlywinks, After Eights and the great outdoors.

“Fast forward 40 years and my parents have taken those familiar recipes, including the marmalades, hot hams and waffles, and imprinted on them their own particular mark. They adore cooking – it is a passion that accelerated when we flew the nest, leaving them the time to experiment. It was about this time that my mother threw down the gauntlet and announced she would no longer cook on Saturday nights. My father met the challenge with his customary mix of feigned amusement and quiet determination. His first Saturday was a day and a half spent in the kitchen grappling with three or four Madhur Jaffrey recipes and the ensuing feast was resplendent, even if it left the kitchen in chaos. His love affair with Heston soon followed and it is from that love that this exquisite fish pie recipe was developed, using my grandmother’s inherited version, my mother’s inherent skill for making simple ingredients sing and my father’s meticulous interpretation of Heston’s perfect mash. My mother does the base of the pie and my father the top, a sinfully delicious mass of silky smooth, mustard-and-Cheddar rich potatoes.

“The result is a jaw-droppingly mouth-watering, deeply pleasing plate of food that restores far more than basic hunger. It is a dish we unconsciously pray for as we walk through the door, now with a small brood of our own, arms reached out for warm hugs and that tumbler of whisky and soda thrust towards us.”

Serves 8

Ingredients

2 medium onions, finely sliced fine sea salt and freshly ground black pepper
½ tsp brown sugar extra virgin olive oil
1kg mixed white fish, skinned
200g smoked, undyed haddock, skinned
400ml full fat milk
about 50 peeled prawns, preferably MSC
3 hard-boiled eggs

For the white sauce:

100g butter
4 heaped tbsp plain or spelt flour
400ml fish stock
anchovy essence, to taste
nutmeg, to taste

For the topping:

1kg peeled floury potatoes
200g very cold butter
200ml full fat milk
3 free-range egg yolks
100g Cheddar, Lincolnshire Poacher or Comté
1 tbsp wholegrain mustard
1 tbsp Worcestershire sauce
2 tsp good quality horseradish sauce

Method

Put a splash of olive oil in a pan, add the onions, sugar and a little salt, and fry gently until caramelised – about half an hour. Cut the fish into even, bite-size pieces.

Bring the milk to the boil, take off the heat, add the fish and leave to cool. Use that milk to make the white sauce, in the usual manner, melting the butter in a pan until sizzling hot, stirring in the flour for a few minutes to cook out its raw taste, then vigorously beating in the milk and stock, little by little, to create a smooth white sauce. Season generously with salt, pepper, nutmeg and the anchovy essence.

Spread the fish in a single layer over the base of a baking dish. Sprinkle evenly with the prawns, followed by the sliced eggs and lastly the onions. Spread the sauce over the top.

To make the mash, cut the potatoes evenly into ½ in slices and rinse in cold water. Heat plenty of water to 80C, add the spuds and cook at a constant temperature of 70C for 30 minutes. Drain and rinse under running water to cool. Put the spuds back into the saucepan with cold salted water, bring to a boil and simmer until completely tender. Drain, return to the pan and dry over a low heat.

Cube the butter into a bowl and press the spuds through a potato ricer onto the butter. Fold spud and butter together, then push through a fine sieve. If eating immediately, heat the milk to a simmer and fold into the spuds (otherwise mix in the milk cold and keep somewhere cool). Mix in the rest of the ingredients and don’t forget to season.

Spread the potato mix evenly over the white sauce. Bake the dish at 180C/160C Fan/Gas 4 (or in the bottom of the top Aga oven) for 30-40 minutes until puffed up and golden.

Thomasina Miers is a chef and founder of the restaurant chain Wahaca, whose books include Meat-Free Mexican

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