Pre-heat oven to 400° F. Use a paper towel to blot the squash and arrange in single layer on a baking sheet lined with parchment paper.
Toss the squash with 2 tablespoons of olive oil, salt, pepper, and fresh thyme leaves and place in hot oven for 30 minutes or until tender.
While the squash is roasting, saute the mirepoix by heating the remaining olive oil and butter in a soup pot, over medium-low heat. Add a few more thyme leaves and saute for 7 to 10 minutes.
When the squash is finished roasting, add it to the soup pot with the mirepoix and then add the warm chicken broth. Simmer for about 10 minutes and then use an immersion blender to blend to desired consistency.
Season with salt and pepper to desired taste. Serve and garnish with additional fresh thyme.
For extra flavor, consider adding a little of the following: