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.
For the Frosting:
Place the vanilla pudding mix into a large bowl and pour in the cold milk. Whisk until combined and starting to thicken. Gently fold in the Cool Whip until it's completely combined. Spread on top of the cooled cake then sprinkle with the crushed gingersnap cookies.
You can serve now, or chill the cake, and serve when chilled. Either way tastes great. Enjoy!