Pumpkin Pie Cake (Todd's Favorite)

Crust:
1 box Yellow Cake Mix (remove 1cup)
1/2 C. margarine
1 egg
Filling:
1 lg. can pumpkin
2/3 C. brown sugar
2 t. cinnamon
1 t. nutmeg
3 eggs
1/4 C. milk
2 t. vanilla
Topping:
1 C. reserved cake mix
1/4 C. margarine (soft)
1/4 C. sugar
1 C. chopped walnuts

Mix cake mix, 1/2 C. margarine, and 1 egg well. Pat evenly in 9X13 greased and floured baking dish. Set aside. In a large bowl mix pumpkin, brown sugar, cinnamon, nutmeg, 3 eggs, milk and vanilla well and pour onto cake mixture. In small bowl mix topping ingredients and crumble over filling. Bake @ 325 for 55-60 minutes. Serve with cool whip. Keep refrigerated.