1.Bring a large saucepan of salted water to the boil. Add fusilli. Cook according to packet directions. Drain and return to pan, covering with a lid.
2.Meanwhile, heat oil in a small frying pan and saute pancetta 4 minutes, until golden. Set pancetta aside until cool enough to handle, then tear into large pieces.
3.Meanwhile, add onion to pan. Cook 5 minutes, stirring. Add garlic. Cook 1 minute. Increase heat to high, add radicchio and water. Cook 4 minutes, until wilted. Add vinegar. Season to taste. Set aside.
4.Add onion mixture to pasta. Toss on high heat 1 minute. Sprinkle with cracked black pepper, to serve.