To make the crust: Combine all the ingredients and mix well with an electric mixer. Pat the mixture into the bottom of a lightly greased 9x13 pan. Prepare filling.
To make the filling: In a large bowl, beat the cream cheese and pumpkin until smooth. Add the eggs, vanilla, and butter, and beat together. Next, add the powdered sugar, cinnamon, nutmeg, and mix well.
Spread over the cake batter and bake for 40-50 minutes. Make sure not to overbake as the center should be a little gooey. Serve with whipped topping.