Instructions:
- Toss cubed squash, onion, and garlic with olive oil, salt, and pepper on a large rimmed baking sheet. Roast at 400°F (200°C) for 35–40 minutes until the squash is fork-tender and lightly caramelized.
- In a large Dutch oven or stockpot, melt the butter (if using). Briefly sauté the grated ginger until fragrant (about 30 seconds).
- Add the roasted vegetables (including any pan juices), stock, nutmeg, and maple syrup (if using) to the stockpot. Bring the mixture to a gentle simmer.
- Carefully use an immersion blender directly in the pot until the soup is perfectly smooth. Alternatively, blend in batches using a standard blender with extreme caution, venting the lid.
- Incorporate the protein source: If using white beans, add them now and simmer for 5 minutes, then blend briefly again. If using Greek yogurt, remove the soup from the heat, temper the yogurt by whisking in a ladleful of hot soup, then slowly whisk the tempered yogurt back into the main pot. Do not boil after adding yogurt.
- Taste the soup and adjust seasoning with salt, pepper, or a squeeze of lemon juice for brightness, if needed.
- Ladle the soup into bowls. Garnish immediately with toasted pepitas and fresh sage ribbons before serving.