Well made fruit pies are glorious! I've tried the pastry made with a whole egg, which makes it a little stronger and easier to deal with, but it is more tender to eat when made just with the yolk.
350g (about 12 ounces) standard flour
Pinch of salt
150g (about 5 ounces) unsalted cold butter, firm but pliable, cubed
100ml (about 3½ fluid ounces) chilled water
1 medium (size 6) free-rang egg, lightly beaten
3 Granny Smith or cooking apples
1 Tbsp lemon juice
250g (about 8½ ounces) frozen or fresh blackberries
¼ tsp ground cinnamon
100g (just over 3 ounces) caster sugar, plus extra for sprinkling on top
2 Tbsp (or 3 Tbsp for frozen berries) cornflour (US cornstarch)
1 egg white, lightly beaten
Ice cream or thickened yoghurt, for serving
1 Preheat oven to 190°C (375°F).
2 Sift flour with a pinch of salt. Put flour and butter in the bowl of a food processor fitted with the chopping blade. Process briefly until mixture resembles coarse breadcrumbs. Mix egg (or just yolk) and water together and pour into the processor through the feed tube. If using just the yolk, increase the water by a tablespoon or so). Pulse together until the mixture gathers in large clumps. Tip dough onto a dry, lightly floured surface and knead until smooth. Wrap dough in plastic food wrap and chill for 20-30 minutes. See here for more information on making pastry Making pastry
3 Peel apples, slice and put them in a bowl. Mix through lemon juice, and add blackberries, cinnamon, sugar and cornflour. Toss gently.
4 Cut off a little more than a third of the dough for the top of the pie. Roll out the rest of the dough on a lightly floured surface and line into a 24cm (9-10 inch) diameter pie plate.
Trim off excess pastry with a sharp knife. Spoon apples and blackberries into pie, mounding them towards the centre. Dampen pastry edge with water.
5 Roll out remaining pastry to a 30cm (12 inch) round on a lightly floured surface, roll pastry around rolling pin and unroll it over the top of the pie.
Trim off excess pastry and crimp edges together by pushing an index finger on one hand under pastry edge and gently squeezing pastry around it with the index finger and thumb of the other hand.
Make a steam hole in the centre of the pie, or cut a large cross with a sharp knife, then brush pie with beaten egg white and dust with caster sugar.
6 Have a baking sheet heating in the bottom third of the oven. Put pie dish on baking sheet and cook for 35-40 minutes, or until pastry is a good golden brown and fruit is tender (if the pastry colours too quickly, drape it with tin foil to deflect the heat). Serve hot with ice cream or warm with thickened yoghurt.
Do not attempt this in a china dish because the pastry on the bottom of the pie will not cook. An enamel pie plate is best because it heats quickly and stays hot and transfers the heat to the pastry.
If using frozen blackberries, increase cornflour (cornstarch) to 3 tablespoons.