Cook the pasta according to the instructions on the packet. Drain and return to the pan.
Meanwhile, heat the olive oil in a pan, then add the onions and garlic. Cook over a medium heat for 8-10 minutes, then add the bacon pieces and continue cooking for 5 minutes until the onions are just starting to turn golden and the bacon is crisp.
Stir the onion and bacon mixture into the pan of cooked pasta. Add the crème fraîche and parsley, and mix to heat through. Season with freshly ground black pepper and serve.