Preheat the oven to 350°F. Combine the carrots, parsnips, onion, and ginger in a shallow roasting pan to fit. Dot with butter and sprinkle with brown sugar. Pour 2 cups of the broth into the pan, cover well with aluminum foil, and bake for 2 hours, until the vegetables are very tender. Transfer the vegetables and broth to a large soup pot with the remaining 6 cups of broth. Season with salt to taste and cayenne pepper. Bring to a boil, reduce the heat, and simmer, partially covered, for 10 minutes. Purée the soup in batches in a blender until smooth, adding more broth if necessary. Return the soup to the pot; adjust the seasonings and heat through. Serve dolloped with crème fraîche and a sprinkling of snipped chives. Kitchen Counter Per serving: 140 calories, 19g carbs, 2g protein, 7g fat, 20mg cholesterol