Roasted Buttercup Squash, Pear, and Ginger Soup

Ingredients

One 2 1/2-pound Buttercup,or other dense squash, rinsed
3 pears, quartered, seeds and stems removed
1 chunk fresh ginger, about 2 inches long, thinly sliced
Olive oil for the squash
Sea salt
2 tablespoons butter 
1 onion, thinly sliced
1/2 cup crème fraîche or sour cream (optional)

Directions

1. Preheat the oven to 425°F.
2. Cut the squash in half, scrape out the seeds, then cut each half into thirds.
3. Put the pieces in a large baking dish with the pears and all but a few slices of the ginger.
4. 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.
5. When the squash is tender, transfer everything from the pan to a cutting board.
6. Add 1 cup water to the pan, and scrape to dissolve the juices, reserving the liquid.
7. Scrape the flesh of the squash away from the skins. You should have about 2 cups.
8. To make a stock, bring 6 cups water to a boil and add the seeds, squash skins, the remaining ginger, and 1/2 teaspoon salt. Lower the heat and simmer, covered, for 20 to 25 minutes.
9. Meanwhile, melt the butter in a soup pot. Add the onion and cook over medium heat, stirring frequently, until it begins to brown a bit, about 10 minutes.
10. Add the pears, ginger, and squash, then the reserved deglazing water.
11. Strain the stock into the pot. Bring to a boil, then lower the heat and simmer, covered, for 25 minutes.
12. Cool briefly, then puree until smooth and pass through a food mill or strainer to ensure a silky texture.