Peel and dice the pumpkin and butternut squash.
Heat a splash of olive oil in a large pot over medium heat.
Add the chopped onion and minced garlic.
Sauté until soft and fragrant, about 5 minutes.
Add the diced pumpkin and butternut squash to the pot.
Stir and cook for about 10 minutes until softened.
Pour in the vegetable broth.
Add the ground cinnamon and nutmeg.
Stir well, then bring the mixture to a boil.
Reduce the heat to low and let it simmer for about 30 minutes.
Check that the squash and pumpkin are tender.
Use an immersion blender to blend the soup until smooth (or carefully transfer to a regular blender in batches).
Stir in the coconut milk.
Let the soup simmer for another 5 minutes.
Season with salt and pepper to taste.
Serve hot, garnished with a swirl of coconut milk or roasted pumpkin seeds if desired.