Preheat oven to 400°F (200°C). Toss cubed butternut squash with 1 tbsp olive oil, salt, and pepper. Spread on a baking sheet and roast for 25 minutes until tender.

In a large pot, heat remaining olive oil over medium heat. Add chopped onion and sauté until translucent, about 5 minutes.

Add minced garlic and cook for 1 minute until fragrant. Stir in cinnamon, nutmeg, and ginger.

Add roasted butternut squash and vegetable broth to the pot. Bring to a boil, then reduce heat and simmer for 10 minutes.

Using an immersion blender, puree the soup until smooth. Alternatively, carefully transfer to a blender in batches.

Stir in heavy cream (or coconut milk) and season with salt and pepper to taste. Simmer for 2 more minutes.

Serve hot, garnished with pumpkin seeds if desired.