1. Heat the oil in a large pot over medium heat.
2. Add the onions and sauté until transparent. Add the garlic, and sauté until the onions are starting to brown.
3. Add the butternut squash, sweet potatoes, potatoes, and the apple.
4. Add water to cover and cook on low to medium heat until the squash is soft.
5. Using an immersion blender, blend until it has an even, creamy, consistency.
6. Add the desired amount of salt and black pepper, and let simmer on low heat for another half hour.
7. Serve hot.