Preheat oven to 375°F. Line and grease a roasting pan.
Cut the butternut squash in half, scoop out seeds with a vegetable peeler or spoon, and place on the pan. Drizzle with olive oil, add a pinch of salt and black pepper. Roast for 45 minutes, until tender.
While roasting, place a large pot over medium heat. Melt butter, then sauté yellow onion and carrots until soft.
Add chicken bone broth and garlic cloves. Simmer gently.
Remove squash skin, add roasted flesh to the pot. Simmer for 30 minutes on low heat.
Use immersion blender (or regular blender, letting soup cool slightly first) to blend into a creamy soup.
Stir in heavy cream, nutmeg, and cinnamon. Season to taste.
Serve hot soup in warm serving bowls with your favorite toppings.