Step 1: Prep the squash. Peel the butternut squash, scoop out the seeds, and cut it into 1-inch cubes. Add the cubes to a 6-quart slow cooker.
Step 2: Sauté the aromatics (optional). Heat the olive oil in a skillet over medium heat. Add the onion and cook for 5 to 6 minutes until soft. Stir in the garlic and ginger and cook 1 minute more, then add everything to the slow cooker. For a dump-and-go version, add the raw onion, garlic, and ginger straight to the slow cooker.
Step 3: Slow cook. Pour in the broth, then add the cinnamon, nutmeg, cayenne, salt, and pepper. Stir, cover, and cook on LOW for 6 to 7 hours or on HIGH for 3 to 4 hours, until the squash is very tender.
Step 4: Add the coconut milk. Stir in the coconut milk, cover, and cook on HIGH for 10 to 15 minutes more, until heated through.
Step 5: Blend. Purée the soup in the slow cooker with an immersion blender until completely smooth. Or blend in batches in a countertop blender, leaving the lid vent open so steam can escape.
Step 6: Adjust and serve. Taste and add maple syrup, salt, or a splash more broth if it’s too thick. Ladle into bowls and top with a swirl of coconut milk and toasted pepitas.