All the flavors of autumn combine in this tasty, nutritious soup. Best of all, the recipe relies on carrot and apple juices as real time savers. For even more convenience, look for peeled and cubed butternut squash in your market's refrigerated case. Parsnips add a mellow undernote, while the ginger contributes a bit of lively heat to the soup, but both items are optional. The soup will keep in the refrigerator, covered, for up to 5 days.
Heat the oil in a large saucepan over medium heat. Add the onion and cook, stirring frequently, until the onion is soft, about 10 minutes.
Add the squash, parsnips, ginger, and stock to the pan. Cover and cook over medium heat until the vegetables are very tender, about 30 minutes. Let the mixture cool slightly, then purée in a food processor. (It may be necessary to do this in batches.)
Return the purée to the saucepan, and add the carrot and apple juices. Reheat slowly over low heat until the soup starts to simmer. Season to taste with salt, pepper, and nutmeg.
To serve, divide the soup among 6 warm bowls. Garnish with a swirl of mascarpone or crème fraîche, if using, and top with a sprinkling of nutmeg. Serve immediately.