"You can give this homely, delicious pie a decadent kick by soaking the raisins in a slug of rum or brandy, draining and adding them to the filling. Serves six to eight."
For the pastry
225g plain flour
A pinch of salt
150g chilled butter, cut into cubes
2 tbsp caster sugar
1 egg yolk
For the filling
4 eggs, slightly beaten
380ml sour cream
200g caster sugar, plus a little extra
Juice of 1 lemon
Finely grated zest of 1 lemon
Finely grated zest of ½ orange
1 tsp vanilla extract
Pinch of salt
Sift the flour and salt into a large bowl and rub in the butter with your fingertips until the mix resembles coarse breadcrumbs. Stir in the sugar. Whisk the egg yolk with three tablespoons of chilled water, sprinkle over the flour and mix in with a knife. Knead very gently into a dough. Wrap in clingfilm and chill for 30 minutes.
Heat the oven to 200C/400F/gas mark 6. On a lightly floured surface, roll out two-thirds of the dough and use it to line a 22cm x 4cm pie dish. Chill for 15 minutes. Keep the remaining dough in clingfilm.
In a large bowl, beat together the eggs. (Set aside a tablespoon's worth for glazing the top of the pie.) Now whisk them with sour cream, sugar, lemon juice and zest, orange zest, vanilla and salt. Stir in the raisins. Roll out the remaining dough into a circle large enough to cover the pie. Pour the filling into the pie, cover with the lid, seal the edges and trim with a sharp knife.
Beat together the reserved egg and a tablespoon of water, and brush this over the top of the pie. Sprinkle with sugar and bake for 20 minutes. Reduce the heat to 180C/350F/gas mark 4 and bake for a further 10-15 minutes – the middle will still wobble a bit as the custardy filling thickens up as it cools. Serve just warm or cold.