Heat olive oil in a large pot over medium heat and sauté onion, carrots, and celery for 6-8 minutes until softened.
Add garlic, thyme, and nutmeg, cooking for 1 minute until fragrant.
Add butternut squash, chicken broth, and water, bring to a boil, then reduce heat and simmer for 20-25 minutes until squash is very tender.
Use an immersion blender to puree the soup until smooth, or transfer in batches to a regular blender and blend until creamy.
Stir in shredded chicken and spinach, cooking for 3-5 minutes until chicken is heated through and spinach is wilted.
Season with salt and pepper to taste and serve hot with crusty bread.