1. Preheat Oven:

Preheat your oven to 425°F (218°C) and line a baking sheet with parchment paper.

2. Prepare Vegetables:

• Cut the butternut squash in half lengthwise and remove the seeds (set them aside for roasting later).
• Peel and roughly chop the onion.
• Slice the top off the garlic head, drizzle with olive oil, sprinkle with salt, and wrap it tightly in foil.

3. Season and Roast:

• Place the squash halves and onion on the baking sheet.
• Drizzle with olive oil, then sprinkle with salt, pepper, sage, and thyme.
• Place the wrapped garlic on the sheet.
• Roast for 45 minutes, or until the squash is fork-tender.

4. Roast the Seeds (Optional):

• While the vegetables are roasting, rinse and dry the reserved squash seeds.
• Toss with olive oil and salt, then spread on a separate baking sheet.
• After removing the vegetables, reduce oven temperature to 350°F (176°C) and roast seeds for 15-20 minutes, stirring halfway.

5. Blend the Soup:

• Once the vegetables have cooled slightly, scoop out the squash flesh and squeeze the roasted garlic cloves from their skins.
• Transfer squash, garlic, and onion to a large pot.
• Add vegetable broth and use an immersion blender to puree until smooth. (Alternatively, blend in batches using a standard blender.)

6. Heat and Serve:

• Heat the soup over medium-low heat until warmed through.
• Stir in the heavy cream (if using) and adjust seasoning to taste.
• Serve hot, garnished with roasted squash seeds and croutons.