Cook the guanciale in a large cold skillet, then turn heat to medium. Cook for 5 to 7 minutes, stirring occasionally, until the fat has rendered and the guanciale is golden and crispy. Remove from heat but leave the fat in the pan.

In a bowl, whisk together the egg yolks, whole eggs, most of the Pecorino Romano, and the black pepper until smooth and creamy. Set aside.

Bring a large pot of salted water to a boil and cook spaghetti until al dente. Reserve 1 cup of pasta water, then drain the pasta.

Add the hot pasta to the skillet with the guanciale and toss over low heat for 30 seconds. Remove the pan from the heat completely, wait 30 seconds, then pour in the egg mixture while tossing vigorously. Add pasta water a splash at a time until the sauce is glossy and coats each strand. Serve immediately with remaining Pecorino and black pepper.