Place rack in center of oven and preheat to 325 dg. Lightly grease a 13 x 9" baking pan with the softened butter or vegetable shortening. Set the pan aside.
Measure out 1/2 C of the cake mix and set aside for the filling.
Place remaining cake mix, melted butter and 1 egg in a large mixing bowl. Blend on low for 2 minutes Scrape down the sides of bowl with spatula. Batter should come together in a ball. With your fingertips, pat the batter evenly over the bottom and 1" up the sides of the prepared pan, smoothing it out with your fingers until top is smooth. Set pan aside.
For the filling, place the cream cheese and condensed milk in the same mixing bowl used to make the crust and and blend about 30 seconds until combimed. Add remaining cake mix, remaining 3 eggs, pumpkin, brown sugar, and spices. Beat on medium for 1 minute then scrape down the sides of the bowl with spatula.
Pour the filling onto the crust and spread so that filling covers the entire surface and reaches the sides of the pan.
Place the pan in oven and bake until cheesecake looks shiny and center no longer jiggles when you shake the pan, about 40 to 45 minutes Remove pan from oven while you prepare topping. Leave the oven on.
For topping, place the sour cream and brown sugar in a small mixing bowl and stir with spoon until well cimbined. Pour topping over the cheesecake and return pan to the oven.
Bake until the topping sets, about 7 to 10 minutes. Remove the pan from the oven and place it on a wire rack to cool, approximately 30 minutes.
Lightly cover the pan with plastic wrap and place the pan in the refrigerator to chill for at least 1 hr., but preferably 24 hours for the flavors to meld. Cut into squares and serve.