Place the flour in a medium bowl and cut in the cold butter with a pastry blender or fork until the mixture resembles coarse crumbs.
Stir in the chopped nuts. Press mixture firmly into a lightly greased 9x13 inch pan and bake for 8-10 minutes.
Remove the pan to a wire rack and let it cool completely.
Cream cheese layer:
In a medium bowl, combine the heavy whipping cream and 1/4 cup powdered sugar.
Beat well with an electric mixer until stiff peaks form.
In another large bowl, beat together the cream cheese and powdered sugar until smooth.
Gently fold in about 3/4 of the sweetened whipped cream (reserving the remaining for topping on the dessert at the end).
Refrigerate the extra sweetened whipped cream until later.
Pudding layer:
In another large bowl combine the dry pudding mixes, milk (if using homemade pudding, don't add the extra 2 cups of milk!), canned pumpkin, and pumpkin pie spice. Stir well to combine.
Once crust is completely cool, smooth the whipped cream cheese layer over the top into an even layer.
Top the cream cheese layer with the pumpkin pudding and smooth into an even layer. Refrigerate, covered, for at least 3-4 hours.
To serve, dollop reserved whipped cream on top, with a sprinkle of crushed pecans.