1Bring a medium pan of salted water to the boil, add the spaghetti and cook accordingly to the packet instructions. Once cooked, drain and set aside.
2In the meantime, fry the bacon in a medium sized pan over a low heat until the fat releases from the bacon. Turn up the heat and cook for about five more minutes, until the bacon starts to colour. Add the leeks and cook for a further 5 minutes.
3Add the crème fraiche and cook until it starts to bubble and reduce slightly.
4Add the lemon juice and zest to your sauce, season with salt and pepper and add the chopped parsley.
5Toss the pasta in the sauce, serve in bowls and sprinkle with Parmesan.