Preheat the oven to 400 degrees. Remove most of the papery skin from the garlic and cut off the tops.
1 head garlic
Place the squash skin side down on a baking sheet and put the head of garlic, cut side up, in one of the butternut squash halves. Drizzle the olive oil over the squash and garlic and roast for 30 minutes, or until the squash is tender.
1 medium butternut squash, 1 tablespoon olive oil
While the squash cooks, make the rest of the soup. Add the chorizo to a medium-sized pot over medium-high heat. Cook, crumbling the chorizo into small pieces, until it is crispy, about 15 minutes - see notes. Remove the crispy chorizo from the pot making sure to leave the oil in the pot.
1 lb fresh chorizo
Add the onion, celery, and carrots to the pot and cook until the vegetables are soft and the onion is beginning to brown. Transfer the vegetables to your blender.
1 large onion, 2 stalks celery, 2 medium carrots
When the squash is cooked, remove it from the oven and let it cool for a few minutes. When it is cool enough to touch, scrape the flesh and put it into the blender. Squeeze the roasted garlic cloves out of the skin and add them to the blender, too.
Add 2 cups of the stock to the blender and blend on high until smooth. Return the soup to the pot and add just enough stock so that the soup is as thick or thin as you would like it to be. Season the soup to taste with salt and pepper then warm the soup for a few minutes before serving it.
4 cups chicken stock
Ladle the soup into bowls and top with the chorizo crispies.
Most chorizo will have enough fat in it to cook properly. If yours doesn't release any oil within a minute or two, add some olive oil to the pan.To make the chorizo crispy, you'll need to cook it well past done. After the chorizo is fully cooked, continue to cook it. It will eventually start to darken and turn very crispy.