Add the guanciale to a cold pan and place over medium-low heat. Let it render slowly until golden and crispy, about 5–7 minutes.
Remove the guanciale with a slotted spoon and set aside.
Reserve the rendered fat — set aside about half for the egg mixture and leave the rest in the pan.
Bring a large pot of salted water to a boil and cook the mezzi rigatoni until just shy of al dente. Reserve at least 1 cup of pasta water before draining.
In a bowl, whisk together the egg yolks, Pecorino Romano, black pepper, and the reserved guanciale fat. Mix until smooth and creamy — thick but pourable.
Add the drained pasta to the pan with the remaining guanciale fat over low heat. Add a splash of pasta water and toss for about 30 seconds.
Turn off the heat.
Add the egg mixture along with a splash of pasta water and about ⅔ of the crispy guanciale. Stir constantly until a silky, emulsified sauce forms.
Adjust the consistency with more pasta water as needed.
Plate the pasta and finish with the remaining guanciale, extra Pecorino Romano, and freshly cracked black pepper.