1-First Step: Mise en place Start by prepping everything so the finish is smooth and quick. Cut the guanciale into 0.5 cm thick slices, then into batons so pieces render and crisp evenly. Measure and finely grate 100g parmigiano reggiano or pecorino romano. Crack the eggs into a large mixing bowl: add 2 whole large eggs and 2 egg yolks, then whisk them with the grated cheese and 1/4 teaspoon freshly ground black pepper until homogeneous. Keep a wooden spoon nearby for vigorous stirring later.

2-Second Step: Cook the pasta Bring 4 quarts (4 liters) of water to a rolling boil. Add 1 tablespoon kosher or cooking salt. Cook 400g spaghetti according to package instructions until al dente; timing will usually be 8-10 minutes depending on brand. Before draining, reserve 1 cup of pasta cooking water (starchy liquid is essential). Then drain the pasta but do not rinse it.

3-Third Step: Render the guanciale While the pasta cooks, place a non-stick pan over medium-high heat. Add the 175g guanciale batons; do not add extra oil. Cook for 4-5 minutes until golden and the fat has rendered. If using garlic, add 1 minced garlic clove in the last minute so it softens without burning. The rendered fat is what will coat the pasta and contribute to the sauce richness.

4-Fourth Step: Coat the pasta in fat When the guanciale is golden, toss the hot drained spaghetti in the pan with the guanciale for 30 seconds to 1 minute so each strand picks up the rendered fat. This step warms the pasta and integrates flavor before emulsifying with the egg mixture.

5-Fifth Step: Emulsify to make the sauce Quickly transfer the hot pasta and guanciale fat into the large bowl with the egg, egg yolks, cheese, and pepper. Add 1/2 cup reserved pasta cooking water right away. This is where timing and temperature matter: the pasta must be hot but not over direct heat, or the eggs will scramble. Stir vigorously with the handle of a wooden spoon for 30 seconds to 1 minute. The motion, combined with starchy water, will thicken the mixture into a creamy sauce that clings to the pasta. If the sauce looks too thick or starts to seize, add a splash more reserved pasta water until it reaches a glossy, silky consistency.

6-Final Step: Plate and serve Serve immediately in warm bowls to keep the sauce creamy and the pasta at the right texture. Garnish with extra finely grated parmigiano reggiano, another crack of black pepper, and a sprinkle of finely chopped parsley if you like. Enjoy while hot.