No added cream.
Bring a large pot of salted water to a boil. Cook 400 g spaghetti until al dente, about 10 minutes. Reserve some of the starchy pasta water before draining.
While the water boils, toast black pepper in a skillet for 2 minutes and set aside.
Cut 200 g guanciale into lardons and cook in a cold skillet over medium heat until the fat renders and the meat is crispy, about 8 minutes. Remove from heat.
In a bowl, whisk together 1 egg and 4 egg yolks and 80 g pecorino romano (finely grated).
Add the drained pasta to the skillet with the guanciale. Turn off the heat and pour in the egg mixture and toss rapidly, adding pasta water a splash at a time until the sauce is glossy and coats every strand.
Crush the black pepper grounds and season generously. Serve immediately.