1. Preheat the oven to 350°F. Halve the squash and scoop out the seeds. Place the squash halves skin-side down on a lightly oiled baking sheet, and then roast until cooked through and soft, anywhere from 30 to 90 minutes (see tips below for cooking times depending on your squash). Remove from the oven and allow to cool.
2. Scoop the flesh of the squash into a large bowl (save any liquid!). Puree the cooled squash with a blender or food processor, adding some of the reserved liquid if needed.
3. In a large stockpot, heat the oil over medium heat and saute the onions until they begin to brown. Add the garlic and cook, stirring often, until the garlic turns light brown in color.
4. Add the stock or water, wine, thyme, bay leaf, and pureed squash, and bring to a simmer. Stir in the remaining ingredients and simmer for 15 to 20 minutes. Taste and adjust seasoning as needed.
Squash cooking times will vary depending on the type and size of squash. At 350°F you can expect these approximate cooking times: