Roast the poblano chiles over high heat on a rack over a stove-top burner. When the skin is charred all over, place the peppers in a paper bag. Leave them for about 10 minutes, then remove and peel the skin -- do not rinse. Discard the stem and seeds, and chop the peppers into a one-fourth-inch dice. Set aside.
In a Dutch oven or small stock pot, combine the butter and oil over medium-high heat. Add the onion and cook until the onion just begins to brown, 6 to 8 minutes.
Add the cubed squash and cook, stirring frequently, until the squash begins to soften, 10 to 12 minutes.
Add the wine and scrape all the cooked bits from the bottom of the pan, and cook until almost all of the wine is absorbed.
Stir in the broth, the diced chiles, the paprika, chile powder, cinnamon and nutmeg, and season with 1 teaspoon salt and one-half teaspoon pepper.
Stir in 3 tablespoons maple syrup and the raisins.
Adjust the heat so the stew reaches a low but steady simmer. Cover and cook, stirring occasionally, until the squash is very soft and tender, an additional 10 to 15 minutes.
Uncover the soup, and ladle 2 to 3 cups broth, with some squash, into a blender. Add the chopped bread and blend until the bread is pureed and the mixture is thickened. Pour back into the Dutch oven, stirring to thicken the stew.
Slowly stir in the cream, and gently heat the stew. Taste and adjust the seasoning as desired. Add the remaining tablespoon maple syrup to sweeten, if needed (depending on the sweetness of the squash) and a few dashes of Tabasco if desired. Remove from heat.
Pour the stew into bowls, and garnishing each serving with a little of the sliced green onion. Serve immediately.