For the pastry
225g plain flour
1/2 tsp of salt
185g butter diced and kept cold
125ml ice cold water
1/2 tsp of lemon juice
For the filling
3 Granny Smith apples
1/2 a lemon
75g golden caster sugar
1 beaten egg
Place the flour and salt into a mixing bowl and add the butter then stir with a large metal spoon.
Mix the water and lemon juice together and pour into the flour.
Using your metal spoon chop the butter up a little while mixing the ingredients together, you want the pastry to have lumps of butter running throughout it.
Bring all the ingredients together to form a pastry then wrap it in cling film. Place the pastry in the fridge and rest for 30 minutes.
Lightly dust a clean work surface with a little flour, then roll out the pastry into a rectangle approximately the size of an A4 sheet of paper.
Brush off any excess flour from the top and fold one third of the rectangle into the centre, then fold the other third over the first one.
Roll out the pastry again and repeat the process, then place the dough into the fridge to rest for 15 minutes.
Rotate the pastry by 90 degrees and roll out and repeat the folds 2 more times, then place it back in the fridge to chill and firm up.
For the filling, peel and core the apples, then cut them into 1cm wide slices.
Squeeze the lemon over the apples, followed by the sugar, give it a careful mix then add the blackberries.
Roll out the pastry into a rectangle approximately 30cm wide by 50cm long, and place all the apple blackberry filling down the middle.
With a sharp knife cut 1cm strips into the pastry on both sides about 10cm into the centre.
Fold over the strips from alternating sides to create a plaited style pattern on top of the filling.
Carefully transfer the pastry plait on to a lined baking tray and brush with the beaten egg to help give it a lovely glaze in the oven.
Bake the plait in a pre-heated oven at 180C for 25-30 minutes until golden brown and crisp.