Cut the guanciale into small, uniform cubes or strips, about 1/2-inch thick. In a medium mixing bowl, whisk together the egg yolks and the whole egg. Add 100g (about 1.25 cups) of the finely grated Pecorino Romano cheese and 1 tablespoon of freshly ground black pepper. Whisk vigorously until the mixture is smooth and well combined. Set aside.

Place a large skillet (preferably non-stick or cast iron) over medium-low heat. Add the diced guanciale to the cold skillet. Slowly render the fat from the guanciale, stirring occasionally, until it becomes golden brown and crispy, about 8-10 minutes. Do not let it burn. Once crispy, remove the guanciale pieces from the skillet with a slotted spoon and set them aside, leaving all the rendered fat in the skillet. Turn off the heat under the skillet.

Bring a large pot of generously salted water to a rolling boil. Add the spaghetti and cook according to package directions until al dente. Just before draining, reserve about 1/2 cup of the starchy pasta water. Drain the pasta well, but do not rinse.

Immediately transfer the hot, drained pasta directly into the skillet with the guanciale fat. Ensure the heat is off or very low to prevent the eggs from scrambling. Pour the egg and cheese mixture over the pasta. Using tongs, toss the pasta quickly and continuously to coat every strand. Gradually add the reserved hot pasta water, a tablespoon at a time, while continuing to toss. The heat from the pasta and the fat, combined with the pasta water, will create a creamy, emulsified sauce. The sauce should be glossy and cling to the pasta, not runny. If the sauce is too thick, add a little more pasta water. If too thin, add a little more Pecorino.

Add most of the crispy guanciale back into the pasta, reserving a few pieces for garnish if desired. Toss once more. Serve immediately in warm bowls, garnished with the remaining crispy guanciale, a generous sprinkle of fresh Pecorino Romano cheese, and extra freshly ground black pepper.