Pumpkin Squares

This is definitely not Julia Child! But this dessert is very tasty and quick to make when you're in a rush.
Source unknown.

Base:
1 x 18 oz package yellow cake mix (reserve 1 cup for the topping)
1/2 cup melted butter
1 egg
Filling:1 x 16 oz can pumpkin
1/3 cup brown sugar
2 eggs
2 1/2 tsp pumpkin pie spice
2/3 cup milk
Topping:
1 tsp cinnamon
1/2 cup chopped walnuts
1 cup reserved topping
1/4 cup butter (optional)

1. Preheat the oven to 350 degrees F.
2. Reserve 1 cup of cake mix for the topping.
3. For the base: combine remaining cake mix, melted butter and one egg in a bowl.
4. Press this mixture over the bottom of a 9" x 13" baking pan.
5. For the filling: combine pumpkin, brown sugar, two eggs, pie spice and milk into a bowl and beat until smooth, and pour over the base.
6. For the topping: combine reserved cake mix, cinnamon, walnuts and cut in the butter in a small bowl; sprinkle over the pumpkin layer.
7. Bake for 40-45 minutes. Cool and serve with creme fraiche or cream.