Preheat oven to 350 degrees
Grease and flour a 13×9 baking dish.
Empty cake mix into a large mixing bowl and remove 1 cup of the cake mix and place in a medium-sized bowl; set aside (you will use this for the topping).
To the remaining cake mix, add 1 stick of butter and 1 egg. Blend with an electric mixer until well-mixed.
Press mixture into prepared baking dish and set aside.
Combine the 2 cans of pumpkin, half & half, 1 cup sugar, 3 eggs, cinnamon, in a large bowl.
Beat together for 3 minutes.
Pour filling onto prepared crust.
Add the remaining 1/4 cup of sugar to the reserved 1 cup cake mix and stir.
Using a pastry cutter or your fingers, knead in the butter and pecans to create the topping.
Evenly distribute the topping for the filling.
Bake for 60-65 minutes at 350 degrees until the center no longer jiggle.
Allow to cool for 20 minutes.
Slice into squares and serve.
Top with whipped cream and sprinkle with chopped pecans. Store leftovers in refrigerator.