Blend together flour, sugar, salt, and butter until mixture resembles coarse meal or pulse in a food processor.
Add 15ml ice water and toss mixture with a fork or pulse until incorporated.
Add enough of the remaining ice water, 10ml at a time, until mixture begins to form a ball.
Turn dough out onto a lightly floured work surface and knead to allow gluten to slightly develop in flour.
Form the dough into a ball and then flatten it to form a disk.
Wrap the dough in plastic wrap and chill for 30 minutes.
In a small bowl blend butter, brown sugar, and flour with your fingertips until smooth and then blend in nuts.
Chill the streusel topping covered until you need it.
Peel and core apples and cut them into thin wedges into a medium bowl.
Toss sliced apples with the remaining filling ingredients to coat.
Preheat the oven to 160ºC / 350ºF / Gas Mark 4.
Roll out chilled dough on a lightly floured surface into a 40 cm round (about 0.4 cm thick).
Place dough into a 25cm deep-dish pie plate letting dough overhang rim.
Spoon filling into pie shell and then fold pastry overhang over filling, leaving center uncovered.
Bake pie in middle of oven 1 hour (pie will not be completely cooked) and remove from oven.
Crumble streusel topping over center of pie.
Brush crust with milk and sprinkle with granulated sugar.
Return pie to oven and bake in the middle of oven 30 minutes more, or until crust is golden.
Remove from oven and cool pie on a rack.
Serve apple pie warm or at room temperature with your favourite ice cream.