In a large bowl, combine the flour, cornmeal, sugar, ginger, cinnamon, and pumpkin pie spice.
Using a grater, grate the cold butter into the flour mixture, mixing until it resembles coarse crumbs.
Remove 3/4 c. of the crumb mixture and set aside. We will use this as the crumb topping.
In another large bowl, whisk together the pumpkin, eggs, molasses, buttermilk, and baking soda.
Add the pumpkin mixture to the flour mixture, stirring until just combined.
Pour the batter into a greased 9-inch springform pan.
Sprinkle the reserved crumb mixture evenly over the batter.
Bake at 350 degrees for 50-60 minutes, or until a toothpick inserted near the center comes out clean.
Cool on a wire rack for 30 minutes before removing sides of the springform pan.
Best served warm. Cut and serve with a drizzle of caramel sauce, if desired.