Prepare the vegetables by peeling, seeding, and cubing the butternut squash and sweet potato into roughly 1-inch pieces. Chop the onion and mince the garlic.
In a large pot over medium heat, warm olive oil. Add the chopped onion and sauté until softened (5-7 minutes). Stir in minced garlic and cook for another minute.
Pour in vegetable broth along with cubed butternut squash and sweet potato. Add spices, salt, and pepper; bring to a boil before reducing heat to simmer for about 20-25 minutes until vegetables are tender.
Blend the soup using an immersion blender or regular blender until smooth.
If desired, stir in heavy cream or coconut milk for extra creaminess. Adjust seasoning as needed.