Wash, peel, and large dice the butternut squash, sweet potato, and onion.
In a large pot, add olive oil and onion and sweat until soft and translucent, about 5 minutes.
Add the butternut squash, sweet potato, cinnamon, nutmeg, salt, and pepper. Stir on medium heat for 5 minutes until vegetables start to soften.
Add in minced garlic and cook for a couple of minutes until fragrant.
Pour in the vegetable broth, bring to a boil, then reduce the heat to low.
Cover the pot and simmer for 25-30 minutes until the squash and sweet potato are fork tender.
Use an immersion blender or carefully transfer soup to a regular blender.
Blend soup until completely smooth and creamy.
Stir int he heavy cream and any additional broth if soup is too thick.
Adjust the seasoning to your taste and serve with a drizzle of cream and toasted sourdough.