Preheat your oven to 200°C (400°F). Peel the sweet potatoes and carrots, then chop them into even 2-3 cm (1-inch) pieces. Toss the vegetables with olive oil, salt, and pepper, spreading them out on a baking sheet. Roast for about 25 minutes, until they are caramelized and tender with a fragrant aroma.
While the vegetables roast, heat a large pot over medium heat. Add a splash of olive oil and sauté the chopped onion until soft and translucent, about 5 minutes, filling your kitchen with a sweet, savory scent.
Once the roasted vegetables are ready, add them to the pot with the sautéed onions. Pour in the vegetable broth to cover the veggies, then bring the mixture to a gentle boil. Reduce the heat and simmer for about 10 minutes to allow the flavors to meld together.
Use an immersion blender to carefully blend the soup directly in the pot until smooth and velvety. Alternatively, transfer the mixture to a blender in batches, blending until silky and uniform.
Taste the soup and adjust the seasoning with salt, pepper, and a pinch of nutmeg if using. Stir in the coconut milk for added richness, warming the soup gently over low heat.
Once heated through, ladle the soup into bowls. Garnish with freshly chopped parsley or cilantro for a burst of fresh flavor and color.
Serve hot, enjoy the comforting warmth and rich caramelized flavors of this simple yet soulful soup.