I based this one on the apple pie recipe I made a little while ago (which I highly recommend!), and it turned out very nicely, and definitely not too sweet for the blackberries we were using.
For the pastry
50g caster sugar (plus a little extra to sprinkle on the top at the end)
350g plain flour (all purpose flour)
For the filling
900g approx cooking apples, I used Bramley but Granny Smith would be fine
300g approx blackberries
125g caster sugar
1/2 tsp cinnamon
35g (4 tbsp approx) plain flour
Make the pastry. Beat the sugar and butter together in a large bowl until just mixed. Add an egg and then just the yolk from the second egg, reserving the white for glazing later. Beat together for about a minute - it will look like scrambled egg, but don't worry! Add the flour in two or three batches, working it in with a wooden spoon, then finishing by gathering it together gently with your hands. Wrap in cling film (saran wrap) and chill for at least 30 minutes.
Peel, core and slice the apples. In a large bowl, mix together the cinnamon, sugar and flour. Add the apples and blackberries, and toss gently to coat evenly.
Preheat the oven to 190°C/fan 170°C/gas 5/375°F. Cut off a third of the pastry and keep it wrapped while you roll out the rest. Line the pie dish, which should be 20-22cm round and 4cm deep, although a flan dish would also work, depending on how deep you want your pie to be.
Fill the pastry case with the apple and blackberries.
Either roll out the remaining pastry and lay on top, making 4-5 small slits (to allow steam to escape) for a solid pastry lid, or make a lattice like I did with the apple pie.
Brush the pastry lid with the egg white, and sprinkle on sugar. A little tip for sprinkling sugar (or anything else), is to do it from high up, not close to the surface - you will get a much more even spread.
You can freeze it at this stage, or just put it in the oven for 40-45 minutes.
Allow the pie to cool for 10 minutes at least, which will help the filling from oozing out when you serve it.
Find more images from this photoshoot at Stocky United.