Put the porcini in a small heatproof bowl with the measurement water, ensuring that the mushrooms are submerged. Leave to soak for 15 minutes. Drain, reserving the soaking water, and squeeze out any excess water.
Heat the olive oil in a large, heavy-based saucepan over a low heat, add the pancetta, onion, carrot and celery and cook, stirring occasionally, for 10 minutes. Increase the heat to medium-high and add the garlic, rosemary and porcini. Cook, stirring, for 1 minute, then add the beans and wine. Boil rapidly until most of the wine has evaporated. Stir in the tomato purée, reserved mushroom soaking water and stock. Bring to the boil, then reduce the heat and simmer gently for 10 minutes. The soup can be prepared ahead to this stage.
Just before serving, bring the soup to a rapid boil and season with salt and pepper. Add the pasta and cook, stirring frequently, until al dente.
Leave the soup to stand for 2–3 minutes before serving with a scattering of Parmesan and a drizzle of extra virgin olive oil.