Preheat oven to 200 degrees Celsius (400 degrees Fahrenheit).

Grate zest from the orange and squeeze the juice.

Add some water to the juice to make up 7 tablespoons of liquid.

In a food processor, mix the butter with the flour and orange zest until it resembles fine breadcrumbs.

Gradually add the orange juice mixture to form the pastry.

Roll the pastry into a ball and refrigerate for at least 30 minutes.

Peel, core, and thinly slice the apples.

In a separate bowl, mix the flour, golden caster sugar, cinnamon, and grated orange zest.

Gently toss the sliced apples in the sugar and spice mixture.

Grease a 9-inch and 2-inch deep pie dish.

Roll out 2/3 of the pastry on a lightly floured surface.

Line the pie dish with the pastry, allowing some to overhang.

Pile the apple filling into the pie dish and press down slightly.

Brush the overhanging pastry with water.

Roll out the remaining pastry and place it on top of the pie.

Press the top pastry slightly to stick to the overhanging pastry.

Trim and neaten the edges with scissors or a knife, leaving them slightly higher than the dish edge.

Pinch the edges together to seal, then flute them with your fingers.

Make two slits on the top of the pie to allow steam to escape.

Brush the top of the pie with the lightly beaten egg white and sprinkle with the remaining golden caster sugar.

Bake for 35 minutes at 200 degrees Celsius (400 degrees Fahrenheit).

Lower the heat to 140 degrees Celsius (275 degrees Fahrenheit) and bake for a further 10 minutes.

Continue baking until the apples are soft and the pastry is golden brown.

Serve warm with whipped cream.