Roasted Carrot Ginger Soup

1 1/2 pounds carrots, peeled and halved lengthwise
1 pound parsnips, peeled and quartered lengthwise (Doesn't "Parsnips" sound like the name of a puppy in a children's book, one of those old Dick and Jane books?)
1 large onion, sliced
3-inch piece of fresh ginger, peeled and chopped
6 tablespoons unsalted butter
3 tablespoons packed dark brown sugar
8 cups rich chicken broth, more if needed (I use some fancy pants highly concentrated French (I think)  stuff I got from Flavour cooking school in Forest Park; you can call them and order some if you want. It's great, very rich, really makes a difference)
salt to taste
pinch of cayenne
1/4 cup creme fraiche, for garnish (I skip)
snipped fresh chives, for garnish (I skip this too)
1.  Preheat the oven to 350. Combine carrots, parsnips, onion and ginger in a shallow roasting pan. Dot with butter and sprinkle with sugar. Pour two cups of broth into the pan, cover well and bake until the vegetables are very tender, two hours. (Your house will smell GREAT.)
2.  Transfer vegetables and every last bit of broth into a large soup pot; add 6 remaining cups of broth. Season with salt and cayenne pepper. Bring to a boil, reduce heat and simmer, partially covered, for ten minutes.
3.  Puree soup in food procesor or with immersion blender  (my personal favorite).
4.  Serve with garnish if desired.