Heat oil and butter on medium heat in a large stock pot. Add the onion and chili powder and cook and stir until the onions are tender, about 8 minutes. Add squash, apples, apple juice, chicken broth, salt and pepper and bring to a boil. Cover and reduce heat, allowing soup to simmer for about 30 minutes and the apples and squash are very soft. Puree in a blender in batches, or use a potato masher to break down the chunks a bit, leaving the soup more rustic (we prefer that!)
Garnish each serving with a sour cream or yogurt dollop and a sprinkle of parsley and croutons.
Note: If the soup has thickened too much after simmering 30 minutes, add a splash of additional cider or broth to bring it to a desirable consistency.