Preheat oven to 400° F. Cut off stem end with a sharp chef’s knife. Microwave the squash for 30–60 seconds to soften slightly, then cut it in half and remove and discard the seeds. Place each squash half, cut side down, in a glass or ceramic baking dish and bake for 30 minutes, until tender.
Melt the ghee in a soup pot and add the onion, garlic, and optional chile pepper. Gently cook over medium heat, stirring now and then so that the onions soften but do not brown.
Sprinkle in the spices and salt, and cook for a minute. Add the coconut milk, water, and flesh from the roasted squash (use a spoon to scoop the squash from the rind, discard the rind). Stir to combine, then simmer gently 15 – 20 minutes to develop the flavors, stirring occasionally.
Remove from heat and purée with an immersion blender. Serve with a dollop of plain yogurt, a few strips of dried mango, and some cashews.