Preheat oven to 400°. Cut the squash in half and scrape the seed cavities clean. Leave the skin otherwise intact. Lightly coat the cut halves of the squash with olive oil and sprinkle with a dash of salt and pepper. Place the squash on a baking sheet lined with parchment paper and roast for 30-40 minutes or until the flesh is fork tender.
When the squash have cooled, remove the flesh from the skins. Purée the roasted flesh, slowly incorporating chicken broth until the mixture is the desired consistency.
Transfer the squash and broth mixture to a large pot and place on the stove over medium-low heat. Add the wild onions, garlic, sage and thyme. Taste for seasoning and adjust with salt and cracked black pepper as needed.
Gently simmer the mixture for 15-20 minutes or until the flavors have melded. Serve hot with a whole sage leaf for garnish.