Preheat the oven to 400°F (200°C).

Toss the cubed butternut squash with 2 tablespoons of melted butter, 1/2 teaspoon salt, and 1/4 teaspoon black pepper on a parchment-lined baking sheet.

Roast the squash for 25-30 minutes, or until the edges are caramelized and the center is fork-tender.

In a large stockpot, melt the remaining 2 tablespoons of butter over medium heat. Add the onion and sauté for 5 minutes until translucent. Add the garlic and cook for an additional 60 seconds until fragrant.

Transfer the roasted butternut squash into the stockpot and pour in the chicken bone broth.

Bring the mixture to a gentle boil, then reduce heat and simmer uncovered for 5-10 minutes to allow flavors to meld.

Remove from heat. Use an immersion blender to puree the soup directly in the pot until completely smooth. Alternatively, transfer to a high-speed blender in batches, ensuring the lid is vented.

Place the pot back over low heat. Whisk in the heavy whipping cream, nutmeg, cinnamon, and the remaining salt and pepper.

Heat through for 2-3 minutes without allowing the soup to reach a rolling boil (to prevent the cream from separating).

Ladle into warm bowls and garnish with roasted pumpkin seeds before serving.