Optional Roasting (Recommended for Enhanced Flavor):

1. Preheat Oven:
   Preheat your oven to 375°F (190°C).
2. Prepare Vegetables:
   Place the butternut squash, sweet potatoes, onion slices, and garlic cloves in a large roasting pan. Drizzle with olive oil, then sprinkle with cumin, cinnamon, chili powder, salt, and pepper. Toss to coat evenly.
3. Roast Vegetables:
   Roast the vegetables for about 30 minutes or until tender and golden around the edges.

Cook the Soup:

1. Transfer or Prepare Vegetables:
   If roasting, transfer the roasted vegetables to a large saucepan. If not roasting, add the prepared (uncooked) vegetables directly to the saucepan.
2. Cook Vegetables:
   Cover the vegetables with water or vegetable stock, ensuring they are fully submerged. Bring to a boil over high heat, then reduce to a simmer. Cook until all vegetables are very tender, about 15-20 minutes.
3. Blend the Soup:
   Use an immersion blender to blend the soup directly in the pot until smooth. Alternatively, transfer the hot vegetables and stock to an upright blender, blend until smooth, then pour back into the pot. (See notes for blending tips.)
4. Add Coconut Milk and Season:
   Stir in the coconut milk, reserving 2 tablespoons for serving. Add the chili flakes, and adjust the seasoning with more salt, pepper, or spices as needed. Add more water or stock to reach your desired consistency if needed.
5. Serve:
   Ladle the soup into bowls, swirl the reserved coconut milk on top, and garnish with fresh chopped coriander. Serve warm and enjoy!