Smoked Pollack and Spinach tart

This is a River cottage favourite. The balance of lightly salty, smoky fish, sweet onion and earthy spinach in a creamy, just-set custard is comfort food nirvana.

Serves 4-6

For the shortcrust pastry
300g plain flour
A pinch of salt
150g cold, organic butter, cut into small cubes
1 egg yolk, plus beaten egg to glaze
About 150ml cold milk

(or start with your own version of a blind-baked shortcrust tart case)

For the filling
300g-350g smoked pollack or haddock fillet
Up to 1 litre whole milk
A knob of butter
2 onions, finely sliced
400g fresh spinach leaves, washed thoroughly and destalked
50g mature cheddar cheese, grated
200ml double cream
2 whole eggs plus 2 egg yolks
Salt and pepper

Start with the pastry. Put the flour, salt and butter in a food processor and pulse until the mixture has the consistency of breadcrumbs. Add the egg yolk then, with the processor running, pour in the milk in a thin stream. Watch carefully and stop adding the milk as soon as the dough comes together. Tip out onto a lightly floured board, knead a couple of times to make a smooth ball of dough, then wrap in clingfilm and chill in the fridge for half an hour.

Preheat the oven to 170C/gas 3. Roll the pastry out thinly and use it to line a 25cm tart tin with a removable base. Trim off any excess pastry and prick the base in several places with a fork. Bake for about 20 minutes, or until the pastry looks dry and cooked. Remove and brush all over with beaten egg, then return to the oven and bake for another 5 minutes or until golden. This helps to seal the pastry and prevent any filling leaking out. Leave the oven at 170C/gas 3.

Put the smoked pollack in a wide pan. Pour in enough milk to just cover the fish, cover the pan and bring to a simmer. You may find this is enough to cook the fish through. If not, keep simmering it very gently for 2-3 minutes, until it will come apart in flakes. Remove the fish from the milk and leave to cool. Don’t discard the milk – strain it and set aside.

While the pollack is cooling, heat the butter in a frying pan over a medium heat and add the onions. Fry gently, until soft and golden brown – a good 10 minutes. Drop the spinach into a pan of boiling water and cook for just a couple of minutes until wilted. Drain and, once cool enough to handle, squeeze dry and coarsely chop.

Flake the pollack into a bowl and add the grated cheddar, onions and spinach. Mix well, then put the mixture into the tart case. Mix 250ml of the strained fish poaching milk with the cream and eggs. Season with salt and pepper and pour over the ingredients mixture in the tart case.

Bake for about 40 minutes, or until lightly set and lightly browned. Leave to cool for a good fifteen minutes. Serve warm or cold.