Heat the olive oil in a large pot over medium heat. Once hot, add the diced onion and sauté for about 5 minutes, until softened.
Add the minced garlic and cook for an additional 1-2 minutes, stirring until fragrant.
Stir in the diced carrots, potato, and butternut squash. Cook for about 5 minutes, stirring occasionally.
Sprinkle the dried thyme over the vegetables and mix well.
Pour in the vegetable broth and bring the mixture to a simmer. Allow it to cook for 20 minutes, or until the vegetables are tender.
Once cooked, choose to blend the soup for a smooth texture or leave it chunky, depending on your preference.
Stir in the pumpkin puree and mix until combined. Season with salt and pepper to taste. If using spinach, add it now and let it wilt in the hot soup.
Serve the soup hot, drizzling heavy cream over each bowl if desired.