Bake (about 40 minutes), microwave (about 12-16 minutes), or pressure cook the pumpkin/squash until barely tender. Meanwhile, cut up the onions, leeks and celery. Saute these along with the garlic in the olive oil until tender. Scoop the squash out of the skin and remove seeds. Cut up the squash into 1-inch chunks and mash about 1/3 of the squash. Add the broth, sugar, salt, and pepper to the sauted vegetables, followed by the beans and squash. Simmer together on low heat for about 10 minutes to blend flavors, but be sure not to overcook, as you want the leeks to remain green. Add water until the soup reaches the preferred consistency.
Serve hot in a hollowed out pumpkin, with crusty bread.