In a large pot, heat the olive oil and butter over medium heat. Sauté the onion, carrots, and celery until softened. Add the apple, squash, rosemary, ginger, and chicken broth. Bring to a simmer and cook until squash is very tender, about 25 minutes. Using an immersion blender (or a stand blender, working in batches), puree the soup until smooth. Add additional water or broth to thin if necessary. Season to taste with salt and pepper.