Grease a 10 cup bundt pan and set aside.

Preheat oven to 350*.

Add butter to mixing bowl and beat until creamy (no lumps).

Slowly add in sugar while beating. Beat one minute.

Beat in one egg at a time, allowing the first egg to incorporate before adding the second. Beat one minute, until airy.

Beat in pumpkin, sour cream and vanilla. Beat 30 seconds after each ingredient.

Stop and scrape bowl. Beat one minute.

Slowly beat in flour, soda, cinnamon and salt, just till combined

To make the streusel, place flour, brown sugar, butter, walnuts, cinnamon, and chocolate chips in a bowl and combine.

Crumble a third of the streusel on the bottom of the pan, then add a third of the batter. Repeat in layering order.

Bake for 45 minutes.

Let cool for half an hour.

Pipe seams of cream cheese frosting.