The secret is very simple, and has nothing to do with adding cream, which many combine for that purpose. Fry the guanciale in a pan without adding more fat or, at most, only a teaspoon of oil, and season the pasta with the egg and cheese cream directly in the same pan where the guanciale has been previously cooked. Once combined, just stir vigorously for one minute: you will see that the eggs tend to become creamy, but without generating the classic "lumps".