Cook spaghetti in salted boiling water until al dente. Reserve 1 cup pasta water and drain.
While pasta cooks, sauté pancetta and garlic in a pan until pancetta is crisp. Remove garlic and discard.
In a bowl, whisk eggs, cheese, and a generous amount of black pepper.
Add hot pasta to the pancetta pan off the heat. Quickly pour egg mixture over pasta, stirring vigorously to create a creamy sauce.
Add reserved pasta water a little at a time if sauce is too thick.
Serve immediately with extra cheese and pepper.