Vegetarian Curry Butternut Squash Soup

1. Melt butter in 4-qt stock pot.
2. Add onion and curry powder. Cover and cook on low heat for 25 minutes.
3. Pour in 2 cups of stock, squash, sweet potatoes,and apples. Bring to a boil and then simmer while partially covered for 25 minutes.
4. Transfer to a food processor equipped with a steel blade and medium disc and add the remaining 1 cup of stock.
5. Transfer back to the stock pot and add apple cider.
6. Season to taste.
7. Optional: garnish with yogurt, sour cream, cheddar cheese, or cilantro.