Preheat your oven to 400F. Spread the kabocha squash, pear pieces, and onion onto two baking trays. Drizzle the pieces with the oil and use your hands to make sure everything is coated. Sprinkle generously with salt and pepper.
Allow the squash and vegetables to roast until the squash is tender and caramelizing (30-35 minutes). Remove peels from the squash by gently scooping the flesh out with a spoon.
Transfer the squash flesh and the roasted pears and onion to a blender. Add 3 cups of broth and ginger and blend till the mixture is smooth. Check for seasonings, and add extra salt and pepper as needed. Add the coconut or soy milk and blend again, till the soup is lighter in color and very creamy.
Return the soup to the pot and add extra vegetable broth if it's too thick for your taste. To serve, divide soup into bowls and drizzle each one with a tablespoon of cashew cream and a sprinkle of pumpkin seeds, if desired.
Leftover soup will keep for up to four days in an airtight container in the fridge, and it can be frozen for up to 1 month.