Roast the squash. Preheat an oven to 425°F (220°). Place cubed butternut squash, onion, and halved garlic cloves on a large rimmed baking sheet (or in a roasting pan). Drizzle with 3 Tbsp olive oil, 1½ tsp Kosher salt, and ¼ tsp black pepper. Place the fresh sage leaves and thyme sprigs on top. Roast for 45 minutes, tossing the vegetables once halfway through.
If using an immersion blender: Discard the fresh herbs, then place roasted vegetables in a large soup pot along with 4 cups of vegetable or chicken broth. Squeeze as much of the roasted garlic in as you like (we recommend ½ head of garlic for moderate garlic flavor and the full head if you really love garlic. The rest can be saved and spread on toast or added to sautéed veggies!). Use an immersion blender to process the soup until very smooth. If using a traditional blender: Working in two batches, discard the fresh herbs, then carefully transfer half of the vegetables into a blender. Squeeze as much of the roasted garlic in as you like (we recommend ½ head of garlic for moderate garlic flavor and the full head if you really love garlic. The rest can be saved and spread on toast or added to sautéed veggies!). Add 2 cups of veggie or chicken broth, then place the lid on top and process until completely smooth. Transfer to a large soup pot, then repeat with remaining ingredients and broth.
Simmer the soup. Place the soup over medium heat, stir in ¼ tsp ground nutmeg, then bring to a simmer and warm through. Taste, adjust seasoning as needed, adding additional Kosher salt and black pepper to taste. While the soup is simmering, cook the pancetta.
Crisp the pancetta. Heat remaining 1 Tbsp olive oil in a skillet over medium heat. Add 6oz cubed pancetta, then cook, stirring occasionally, until the fat has rendered and the pancetta is crispy on all sides, about 5-8 minutes. Do not let it burn, it should still be a little bit chewy in the center. Use a slotted spoon to transfer to a paper towel lined plate.
Garnish, then serve. When ready, divide the roasted butternut squash soup into individual bowls. Drizzle with either 1 tsp heavy cream or 1 tsp of extra virgin olive oil (if making dairy-free). Add a few crispy pancetta cubes on top, then garnish with additional black pepper and a few thyme leaves. Enjoy immediately!