Heat the butter in a medium pan and cook onion, celery and carrots until tender.
Transfer the mixed vegetable into a slow cooker and add squash, vegetable broth, turmeric powder, cayenne powder and a dash of nutmeg.
Cook for 4 hours, or on low heat for 7-8 hours.
About 1 hour before serving time, transfer the squash and vegetable chunks mixture into blender. Blend until smooth and return the mixture back to slow cooker.
Season with salt and pepper to taste.
Optional: use 1 teaspoon maple syrup or more to add sweetness.