In a large saucepan or Dutch oven, cook bacon until crisp; crumble and set aside.
Drain all but 1 tablespoon drippings; saute onion and garlic in dripping until tender.
In a blender or food processor, puree squash, flour, 1/3 cup milk and onion mixture; add to pan.
Add the broth, curry powder, salt, pepper, nutmeg and remaining milk; bring to a boil over medium heat. Boil for 2 minutes. Top servings with a dollop of sour cream if desired.