In a 6 quart slow cooker, combine 8 cups cubed butternut squash, ½ finely chopped white onion, 5 cloves minced garlic, and 5 cups vegetable stock. Cover and cook on high for 2 hours or on low for 4 hours, or until squash is very tender.
Transfer contents of the slow cooker to a blender or use an immersion blender to blend until smooth.
Stir in ½ cup shaved parmesan cheese, cover for another 5-10 minutes until cheese is melted. Stir in salt and pepper to taste and serve. Sprinkle with optional fresh herbs for garnish