Cook the spaghetti in salted water according to package directions until al dente. Meanwhile, fry the bacon in a dry pan until crispy, then set aside.
Clean the leeks, wash and cut into fine rings. Peel the garlic and chop finely. Heat the butter in a frying pan and sauté the leeks in it.
Add the garlic and pour the cream, bring the sauce to a boil and simmer for 5 minutes.
Mix the hot drained pasta with the sauce. Season with pepper, divide among 4 plates and serve sprinkled with Parmesan cheese and the crumbled crispy bacon.
