1. Cook the Pasta: Bring a large pot of salted water to a boil. Add the pasta and cook until al dente, according to the package instructions. Reserve about 1 cup of the pasta cooking water, then drain the pasta
2. Prepare the Sauce: In a bowl, whisk together the eggs, egg yolk, Pecorino Romano, and Parmesan cheese until well combined. Season with a generous amount of black pepper
3. Cook the Guanciale: In a large skillet, cook the guanciale over medium heat until it becomes crispy and golden brown. If using garlic, add it to the pan and cook until fragrant, then remove and discard the garlic
4. Combine Pasta and Guanciale: Add the drained pasta to the skillet with the guanciale. Toss well to coat the pasta in the rendered fat. Remove the skillet from the heat
5. Add the Egg Mixture: Pour the egg and cheese mixture over the pasta, tossing quickly to combine. The residual heat from the pasta will cook the eggs gently, creating a creamy sauce. If the sauce is too thick, add a splash of the reserved pasta cooking water to achieve the desired consistency
6. Serve: Divide the pasta among serving plates. Garnish with additional grated Pecorino Romano, a sprinkle of fresh parsley, and more black pepper
