1. Preheat the oven to 425°F. Cut the squash in half, scrape out the seeds, then cut each half into thirds. Put the pieces in a large baking dish or roasting pan with the pears and all but a few slices of the ginger. Brush with oil, season with salt, and bake until fragrant and tender, about 1 hour. Turn the pieces once or twice so that they have a chance to caramelize on more than one surface. If the squash seems very dry (some varieties are), add 1 cup water to the pan to create steam and cover with foil. When the squash is tender, transfer everything from the pan to a cutting board, add 1 cup water to the pan, and scrape to dissolve the juices, reserving the liquid. Scrape the flesh of the squash away from the skins. You should have about 2 cups.
2. To make a stock, bring 6 cups water to a boil and add the seeds and, eventually,the squash skins, the remaining ginger, and 1/2 teaspoon salt. Lower the heat and simmer, covered, for 20 to 25 minutes.
3. Meanwhile, melt the butter in a soup pot. Add the onion, give it a stir, and cook over medium-low heat, stirring frequently, until it begins to brown a bit and is fragrant, about 10 minutes. Add the pears, ginger, and squash, then the reserved deglazing water. Strain the stock into the pot. Bring to a boil, then lower the heat and simmer, covered, for 25 minutes. Cool briefly, then puree until smooth and pass through a food mill or strainer to ensure a silky texture. Serve as is or swirl in the crème fraîche.
From Vegetable Soups From Deborah Madison's Kitchen by Deborah Madison Copyright (c) 2006 by Deborah Madison. Published by Broadway Books.Deborah Madison's Vegetarian Cooking for Everyone and The Savory Way, each earned the IACP's Julia Child Cookbook of the Year award. Vegetarian Cooking for Everyone also received a James Beard Award, as did Local Flavors, her most recent book. She is also the author of the James Beard Award nominee This Can't Be Tofu! and The Greens Cookbook, which is now a classic. She lives in Galisteo, New Mexico.