Sour Cream Apple Pie

Again, compliments of Our Patisserie (is it any wonder this is my favorite blog?) I doubled the crust because I had to use a larger pan, and if I'd thought about it I would have halved-again the apples and cream. Unfortunately I don't have a cross-section picture but I'll have a taste-test result here soon!
Crust:
* 1 1/2 c graham crackers, finely ground
* 8 tbs melted butter (or enough to make it stick)
* 3/4 c ground pecans
Filling:
* 3/4 c sugar
* 2 tbs flour
* 1 c sour cream
* 1 egg
* 1 tsp vanilla
* 1/4 tsp cinnamon
* 5 large apples, peeled, cored and sliced thinly
Topping:
* 3 oz chopped walnuts
* 1/2 c packed brown sugar
* 1/2 tsp vanilla
* 1/2 tsp cinnamon
* 4 oz butter, cut into tiny pieces
* 1 1/2 c all-purpose flour

Preheat oven to 350F. Combine the crust ingredients well and press into a 9-inch springform pan.

Mix all the filling ingredients except the apples in a large bowl until well combined. Add the sliced apples and mix well. Pour into the crust and bake 30 minutes.

Meanwhile, prepare the topping. Place all the topping ingredients in the food processor bowl and process just until crumbly. (Of course, if your food processor is small like mine, you can do this the old-fashioned way. Mix sugar, flour, cinnamon and vanilla in a bowl, cut in the butter using a pastry blender until crumbly and add the chopped walnuts.) Sprinkle the topping on the partially baked filling and bake for another 15-20 minutes.

UPDATE: The taste-test results are in, and it's a success! There were comments about how it was a bit runny, so next time I'll probably add a bit more sour cream and a little cornstarch, and bake it for ~5 more minutes.