Frozen sour cherry & berry pie

Mix the plain flour and icing sugar in a large bowl, then finely grate in half the orange zest. Chop the butter into cubes, then rub in with your fingertips until the mixture resembles fine breadcrumbs. Remove one quarter of the mixture (about 2 big handfuls) to a separate bowl.Back to the main bowl: beat and stir in 1 egg and 1 yolk (reserving the white), then gently scrunch the dough into a ball – be careful not to overwork it. Wrap and rest in the freezer for 30 minutes.Drain the pears and put aside, reserving the juice. Pour the juice into a large casserole pan with the vanilla and finely grate in the remaining orange zest. Add the pears, frozen berries and sugar, and bring to a simmer, stirring constantly, then stir in the cornflour. Bring to a boil then gently simmer for 5 minutes, stirring constantly, until thickened slightly. Remove from the heat and allow to cool to room temperature.When you’re ready to bake, grease a deep 26cm non-stick loose-bottomed tart tin. Use a box grater to coarsely grate in the pastry, using your fingertips to press it into the base and up the sides, letting it bulge up a centimetre above the brow of the tin (don’t worry if it’s not perfect, just try to create a fairly even layer), then brush with the reserved egg white.Preheat the oven to 180°C/350°F/gas 4 and place a large baking tray at the bottom of the oven. Spoon the cooled fruit into the pastry case and scatter over the crumble topping, leaving a little border at the edges. Transfer to the tray and bake for 45 minutes, or until golden and bubbling, then let it sit in the tin to firm up. When you’re ready to serve, enjoy with scoops of vanilla ice cream.