Preheat your oven to 400°F (200°C). Spread the peeled and chopped butternut squash and carrots on a baking sheet, then drizzle with olive oil and toss to coat evenly. Roast for about 35-40 minutes, until the vegetables are tender and slightly caramelized around the edges, filling the kitchen with a sweet aroma.
While the vegetables roast, sauté the diced onion and minced garlic in a large pot over medium heat with a drizzle of olive oil until the onion becomes translucent and fragrant, about 5 minutes.
Add the roasted vegetables to the pot with the sautéed onion and garlic. Pour in the vegetable broth and bring the mixture to a gentle simmer.
Use an immersion blender directly in the pot or transfer the mixture to a blender to puree until completely smooth and velvety. Return to the pot if needed, and stir in the ground nutmeg, salt, and pepper to taste.
Warm the blended soup for a few minutes over low heat, adjusting the seasoning as desired. If using cream or coconut milk, swirl it in now for added richness.
Serve the soup hot, garnished with a drizzle of cream or coconut milk if desired, and enjoy the cozy, velvety smoothness of this seasonal dish.
