Heat the oil in a large, deep pan, then add the celery, onions, garlic, sage and rosemary, season generously and cook, stirring occasionally, for 15-20 minutes, until soft.
Stir in the squash, potato, tomatoes, chilli and parmesan rinds (if using), season again, and add just enough boiling water to cover. Pop a lid on the pan and simmer gently until the squash is very soft – about half an hour.
Meanwhile, bring a pan of salted water to a boil and cook the pasta until al dente. Drain, then rinse under cold water to prevent it sticking.
Once the squash is soft, use a hand blender or potato masher to break down the squash and potato, but leave a few chunks for extra texture.
Stir in the pasta and add enough boiling water to create your perfect soup-like consistency. Stir in the vinegar, adjust the seasoning to taste, and keep warm.
To serve, gently warm the oil on a medium-high heat, then fry the sage leaves for two minutes, turning them once, until crisp. Lift out the leaves, and keep the oil for drizzling over the soup.
Ladle the soup into bowls, and top with the crisp fried sage, some of the sage oil, more good extra-virgin olive oil, if you wish, and some grated parmesan.