Preheat your oven to 400°F (200°C). Halve the acorn squash, scoop out the seeds, brush with olive oil, and season with salt and pepper. Roast for 30-40 minutes until tender.

While the squash roasts, heat remaining olive oil in a Dutch oven over medium heat. Add onions, carrots, and celery, sauté for 5-7 minutes until softened. Stir in minced garlic and sauté for an additional 1-2 minutes.

Remove the roasted squash from the oven, scoop the flesh into the pot with sautéed veggies. Pour in vegetable stock, add sage, thyme, and rosemary. Stir gently to combine.

Bring the mixture to a simmer over medium heat and cook for 20-30 minutes. Use an immersion blender to puree the soup until smooth.

After blending, stir in the half and half cream and adjust seasoning with salt and pepper. Serve warm, topped with your choice of optional toppings.