- Place ginger root and 1/4 cup sugar in food processor bowl with knife blade attachment; pulse until ginger is finely minced then add 1/4 cup flour and pulse a couple of times. Remove 3 Tablespoons of this ginger paste to use in pastry.
- Add brown sugar and 1/2 cup flour to remaining ginger paste and pulse to blend.
- Add 1/4 cup butter pieces. Pulse until mixture resembles coarse crumbs.
- Remove from processor bowl, stir in walnuts and set aside.
- Combine flour and salt in food processor with knife blade attachment and process for about 10 seconds.
- Add cold butter cubes; process by pulsing 8 to 10 times or until most of the butter is about pea-sized. Do not over mix.
- Add reserved ginger paste.
- Add water through food chute with processor running. Add only enough water to moisten so dough begins to clump.
- Form into a 4-5 inch disk, place in a food storage bag and refrigerate for 30 minutes before rolling.
- Roll out dough on a lightly floured surface, into a 12-inch round; fit pastry into a 9-inch pie pan. Freeze crust before filling.
- Preheat oven to 425°F.
- Wisk together all ingredients until well blended.
- Pour into frozen prepared pie shell.
- Bake 20 minutes. Reduce temperature to 350°F; bake 20 minutes.
- Sprinkle topping over pie; bake until pie is set and topping is golden 20 to 25 minutes. Cool completely before slicing.