Apple-Cinnamon Custard Pie

This recipe is from a cookbook that I got when when I got married. It is called Portland's Palate and it is a delicious collection of recipes from Portland, Oregon.

Crust:
1 3/4 C. All-purpose flour, sifted
1/4. C. granulated sugar
1 t. cinnamon
2/3 C. butter
1/4 C. cold water

Filling:
1 egg
1 1/2 C. sour cream
1 C. granulated Sugar
1/4 C. all-purpose flour
2 t. vanilla extract
1/2 t. salt
2 1/2 lbs Macintosh apples, pared, quartered, cored and sliced*

Topping:
1/2 C. butter, room temperature
1/2 C. all-purpose flour
1/3 C. granulated Sugar
1/3 C. brown sugar, firmly packed
3 t. cinnamon
1 c. walnuts, coarsely chopped

Crust:
In a large bowl or food processor fitted with the dough blade attachment, combine the flour, sugar and cinnamon. Cut in the butter (if using the bowl: use a pastry blender to evenly distribute the butter) until the mixture is the consistency of corn meal. Sprinkle in just enough water to moisten the dough. More or less water may be needed.

Pre-Heat oven to 450 degrees
Roll out the dough on s lightly floured surface to a 12-inch diameter circle. Fit into a 10 inch pie plate. Fold under overhanging pastry flush with rim. Flute to make a stand-up edge. Chill until ready to fill.

Filling:
In a large mixing bowl, beat egg slightly. Stir in sour cream, sugar, flour, vanilla and salt until mixture is smooth. Add sliced apples**, stirring gently just to coat apples. Spoon filling into shell.

Bake at 450 degrees for 10 minutes, lower the temperature to 350 degrees and bake 35 minutes longer. While pie bakes prepare the topping.

Topping:
In a small bowl, combine butter, flour, sugar, brown sugar, cinnamon and walnuts. Blend well.

Remove pie from oven and sprinkle topping evenly over filling. Return to oven.

Bake for 15 minutes longer or until topping is lightly browned. Cool pie on a wire rack.

Notes:
* For whatever reason, I always have a hard time finding Macintosh apples so I have used Fuji and Braeburn (I think Braeburn is my favorite). Just look for an apple that bakes well and that has a firmer texture, also make sure that it is a little tart - but it doesn't have to be sour (like a Granny Smith).
** Make the custard before you peel and slice the apples. Then as you slice the apples you can place them directly into the custard preventing them from browning. I know they say to place them in a bowl of ice water with lemon juice but they end up absorbing too much water and then you have a watery pie. no bueno.