01 - Preheat oven to 400°F.
02 - In a large bowl, toss sliced apples with lemon juice, granulated sugar, cinnamon, and flour. Gently fold in blackberries.
03 - Line a 9-inch pie dish with half the pastry, pressing into edges and trimming excess.
04 - Spoon fruit filling evenly into the pastry-lined dish.
05 - Roll out remaining pastry and cover the filling. Trim and crimp edges to seal. Cut small slits on top for steam release.
06 - Brush top with beaten egg and sprinkle with demerara sugar.
07 - Bake for 45–50 minutes until crust is golden and filling bubbles.
08 - Allow pie to cool 10–15 minutes before serving warm.