Heat oil over medium heat in a 6-quart stockpot. Add onions and garlic and saute until soft but not brown, about 6 to 7 minutes. Add the butternut squash, broth, curry powder and salt and bring to a boil. Reduce heat and simmer until squash is tender, about 12 to 15 minutes. Remove from heat stir in honey and puree with an immersion blender or in batches in a blender until smooth. Season with salt, to taste.
Ladle into serving bowls and add a dollop of yogurt.