Preheat oven to 350 degrees F.
Halve squash and place cut side up in a baking pan with 1/2" of water. bake uncovered for about 45 minutes. Squash won't be fully cooked, but slightly tender. Cool.Using a vegetable peeler, peel of outer skin and scrape inside to remove seeds and stringy fibers. Cut into cubes. Should yield about 6 cups. (I think you can actually cheat on this and get pre-cubed squash in the produce section of your market).
In a Dutch oven or large pot heat butter and oil until hot and shimmering. Add shallots and stir, for a minute or two, then add garlic and stir. Next, add squash and broth and bring to a boil. Add thyme and bay leaf, reduced heat and cover. Simmer on low about 45 minutes until squash is tender. Remove bay leaf and thyme sticks, if there are any
Puree soup using an immersion blender or upright blender, until smooth.
Return soup to pot, add half and half or cream to thin to desired consistency. Finish with toasted, chopped cashews and a drizzle of cream.