Cut the pumpkin into large chunks, and place on a parchment or foil-lined baking sheet. Drizzle with oil and roast at 200˚C until fork-tender and golden.
In a blender mash the roasted pumpkin until smooth. Transfer into a soup pot.
Add cream, sour cream, wine and vegetable stock, stir and combine.
Bring the soup to a boil, then immediately remove from the flame.
Sprinkle with chopped fresh sage leaves and serve with croutons.