Boil a large pot of water. Once at a boil, heavily salt the water. Cook spaghetti until al dente.
In a nonstick pan, fry guanciale on medium heat for 8 minutes or until the fat is rendered and the meat is slightly crispy. Remove the guanciale from the pan and set aside.
Add ¼-1/2 cup of pasta water to the guanciale oil and combine. Add the pasta to the saucepan and mix. Remove the pan from the heat to cool for a moment.
Combine eggs and pecorino by scrambling. Stir the egg and pecorino mixture into the pasta vigorously, constantly moving the pasta around. Slowly add pasta water a little at a time until the sauce is slightly creamy. Add black pepper.
Remove from the pan and transfer to a bowl to avoid cooking the egg. Serve with extra pecorino.
Notes
Always cook meat like guanciale or pancetta starting from a cold pan. This will help render the fat slowly while developing a crispy texture.
When you're first learning to make carbonara, it can be helpful to cook it in a nonstick pan because it doesn't hold heat as well and will be more forgiving if the temperature gets too high.