Preheat oven to 350 degrees F.
Prepare box of cake mix according to package instructions, then pour into a lightly greased 9"x13" cake pan. DO NOT BAKE. Set aside.
In another bowl whisk together the ingredients for the Pumpkin Pie (pumpkin, evaporated milk, cream, eggs, brown sugar, and pumpkin pie spice), until smooth. Slowly pour the pumpkin pie mixture all over the cake mix.
Carefully place cake into the oven and bake for 50-60 minutes or until the center is no longer jiggly, and a toothpick inserted into cake mix comes out clean. Let cool to room temperature.
Make the topping:
Pour heavy cream and powdered sugar into a mixing bowl with the whisk attachment. Beat on medium-high until stiff peaks form.
Whisk together the French Vanilla pudding mix, pumpkin pie spice and cold milk. Whisk until pudding begins to thicken.
Gently fold pudding mixture into the whipped cream until it's completely combined. Cover and refrigerate until cake is completely cooled.
Spread on top of the cooled cake.