Preheat the oven to 180C (160C fan, 350F, Gas mark 4)
Place the apples in a medium pan with soft brown sugar. Cook over a medium heat for 5 minutes, or until the apples are soft. Set aside to cool for 5 minutes. Stir in the blackberries and vanilla extract.
Cut the pastry into six 10cm rectangles. Using a slotted spoon, divide the fruit mixture equally between half the pastry rectangles, leaving a 1-2cm border.
Brush the borders of the topped pastry rectangles with the beaten egg. Place the remaining pastry pieces over the top, pressing the edges down with a fork to seal in the filling.
Make 2 slits in the top of each pie to let the steam escape.
Brush the parcels with the beaten egg and sprinkle with the demerara sugar, if using. Bake for 25 minutes or until golden and cooked through. Leave to cool for 5 minutes and transfer to a wire rack.
Blackberry and apple parcels (from the Little Dish Family Cookbook) https://www.amummytoo.co.uk/blackberry-apple-parcels/