Preheat oven to 375°F. Cut a large slice off the pumpkin about 1-inch from the stem end, and reserve. Clean out seeds. Cut a thin slice off the bottoms, if necessary, to make an even base. Brush bowls and tops with oil and sprinkle salt inside. Place bowls and tops, stem side up, in a large baking pan. Bake until flesh is tender, about 1 - 1 1/4 hr. When cool enough to handle, scoop out flesh, leaving a thick wall. Reserve flesh for the soup.

Heat olive oil in a large saucepan over medium-high heat. Add onion and apple and cook, stirring, until onion is golden, about 8 minutes. Add cider and cook until syrupy, about 3 minutes. Add broth and bring to a boil. Simmer until onion and apple are very tender, about 20 minutes.

Add reserved pumpkin flesh to soup and puree in batches in a blender. Return to saucepan and stir in cream. Add cheese and stir over medium heat until cheese is melted. Season to taste with salt and pepper.

Serve soup in roasted pumpkin shells with tops alongside. Garnish with chopped scallions.