Preheat oven to 350 degrees F. Spray a 12 cup bundt pan with flour-added cooking spray.
In a mixing bowl, beat softened cream cheese and both sugars until smooth. Stir in eggs, pumpkin, cornstarch, vanilla and pumpkin pie spice or spice combo. Pour into bundt pan and bake for 15 minutes.
While pumpkin mixture bakes, combine cocoa and chocolate in a small saucepan; pour hot coffee over chocolate and whisk until smooth - if coffee is not hot enough to melt chocolate, turn heat to medium and heat just enough so that chocolate melts; Remove from heat (if using) and whisk in sour cream.
In a second bowl, whisk together flour, salt, and baking soda. Using electric mixer, beat butter, brown sugar, and vanilla on medium-high speed until pale and fluffy, about 3 minutes. Add eggs and continue beating for another minute.
By hand, stir 1/3 of the flour mixture into batter. Add half of the chocolate/sour cream mixture and stir until incorporated. Scrape bowl and add remaining flour mixture and all of remaining chocolate mixture.
Remove bundt cake pan from oven and quickly pour chocolate mixture over pumpkin. Return to oven and bake for 42 minutes or until wooden skewer inserted into center comes out with few crumbs attached.
Cool in pan 30 minutes, then invert cake onto parchment paper or cake plate. Let cool at room temperature for 1 hour, then transfer to refrigerator to chill.
Before serving, drizzle with dulce de leche or caramel sauce.
Store cake in refrigerator.