Steusel Topped Pumpkin Pie

15 oz can Pumpkin (not pumpkin pie filling)
Pie Ingredients:
14 oz can Sweetened Condensed Milk
1 Egg
3/4 tsp Cinnamon
1/2 tsp Ginger
1/2 tsp Nutmeg
1/2 tsp Salt
1 Graham Cracker Pie Crust

Topping Ingredients:
1/4 c. Brown Sugar
1/2 tsp Cinnamon
2 TB Flour
2 TB Cold Butter
3/4 c. Walnuts, chopped

Preheat oven to 425 degrees.  Combine pie ingredients and pour into graham cracker pie crust.  In a small bowl combine the topping ingredients and set aside.  Bake the pie without any topping for 15 minutes.  Reduce oven to 350 degrees, then sprinkle topping over pie and return to oven to bake for an additional 40 minutes.