Rehydrate porcini in a small bowl with 150ml boiling water for 5 minutes.
Heat olive oil in a large saucepan over medium-high heat, add pancetta and fry until browned (3-5 minutes). Add onion and garlic and sauté, stirring occasionally, until tender and just golden (5-7 minutes). Add wine and cavolo nero and cook until wine is reduced and cavolo nero wilts (3-5 minutes).
Meanwhile, cook pasta in a large saucepan of salted boiling water until al dente (10-12 minutes). Drain, add to cavolo nero and season to taste.
Drain porcini, reserving a little water, chop and add to pan with a few splashes of porcini water to loosen the pasta. Gently combine and serve hot topped with a drizzle of extra-virgin olive oil and plenty of parmesan.