In a large skillet, cook the pancetta or guanciale over medium heat until crisp and the fat has rendered. Remove the meat with a slotted spoon and set aside on a paper towel-lined plate. Leave about 2 tablespoons of rendered fat in the skillet.

Meanwhile, bring a large pot of generously salted water to a boil. Add the spaghetti and cook according to package directions until al dente.

While the pasta is cooking, whisk together the whole eggs, egg yolk, grated Pecorino Romano, and freshly ground black pepper in a medium bowl.

Before draining the pasta, reserve about 1 cup of the starchy pasta water.

Drain the spaghetti and immediately add it to the skillet with the rendered fat. Toss to coat.

Remove the skillet from the heat. Gradually pour the egg and cheese mixture over the hot pasta, tossing continuously. The residual heat from the pasta will cook the eggs and create a creamy sauce. Add about 1/4 cup of the reserved pasta water to help emulsify the sauce. Continue tossing and adding more pasta water, a tablespoon at a time, until the sauce reaches your desired consistency.

Stir in the reserved crispy pancetta or guanciale. Taste and adjust seasoning with salt and pepper if needed.

Serve immediately, garnished with additional grated Pecorino Romano and black pepper.