Bring a large pot of salted water to a boil. Cook spaghetti according to package directions until al dente.

While pasta cooks, crisp guanciale in a large skillet over medium heat until golden and its fat is rendered. Remove crispy guanciale from the pan, leaving the rendered fat.

In a bowl, whisk together egg yolks, whole eggs, finely grated Pecorino Romano, and a generous amount of freshly ground black pepper until smooth. Do not add salt to this mixture as guanciale and Pecorino are salty.

Before draining pasta, reserve about 1 cup of pasta water. Drain spaghetti and immediately add it to the skillet with the rendered guanciale fat (off the heat to prevent eggs from scrambling).

Quickly add the egg and cheese mixture to the hot pasta, tossing vigorously to combine. Add a splash of the reserved pasta water as needed to create a creamy, emulsified sauce. The residual heat from the pasta will cook the eggs without scrambling them.

Stir in the crispy guanciale. Taste and adjust seasoning with more black pepper if desired. Serve immediately with extra Pecorino Romano cheese on top.