In a large skillet melt the butter over a medium flame, then stir in the onion, butternut squash, brown sugar, and cinnamon, combining well.
Cover skillet and allow ingredients to saute for 20 – 25 minutes until tender, stirring occasionally.
Once the butternut has tenderized, add the vegetable broth, cayenne pepper, nutmeg, and salt & pepper to the skillet, then cover once more and allow everything to simmer for 5 minutes. When ready, transfer mixture to food processor or high-powered blender, then blend until smooth. Pour the soup back into the skillet, then lastly stir in the milk (add more salt here if needed). Reduce flame to low and keep soup warm.
When ready serve the butternut soup with additional drizzles of coconut milk and fresh thyme, if desired.