Preheat your oven to 400°F (200°C).

Place the cubed butternut squash on a baking sheet and drizzle with olive oil. Toss to coat the squash evenly.

Roast the butternut squash in the preheated oven for about 30-35 minutes, or until it is tender and lightly caramelized. Make sure to toss the squash halfway through to ensure even cooking.

In a large pot, melt the butter over medium heat. Add the chopped onion and minced garlic cloves. Sauté until the onion is translucent and fragrant.

Add the roasted butternut squash to the pot and stir to combine with the onion and garlic.

Pour in the vegetable broth and bring the mixture to a boil. Reduce the heat to low and let it simmer for about 15 minutes to allow the flavors to meld together.

Using an immersion blender or a regular blender, puree the soup until smooth and creamy. If using a regular blender, work in batches and be careful when blending hot liquids.

Return the soup to the pot and stir in the heavy cream. Season with ground nutmeg, salt, and black pepper. Adjust the seasoning according to your taste preferences.

Simmer the soup for an additional 5 minutes to allow the flavors to meld together. If the soup is too thick, you can add more vegetable broth or water to achieve your desired consistency.

Serve the butternut squash soup hot, garnished with a drizzle of cream, a sprinkle of nutmeg, and some freshly chopped parsley or chives.