Prep the pasta water. Bring a large pot of salted water to a boil. It should taste like the sea. This is crucial for well-seasoned pasta and a balanced sauce.

Whisk the sauce base. In a medium bowl, whisk the eggs, egg yolk (if using), and cheese until smooth and thick. Add a generous amount of freshly ground black pepper. Set aside.

Cook the pasta. Drop the spaghetti into boiling water and cook until just shy of al dente. Reserve at least 1 cup of pasta water before draining.

Crisp the bacon. While the pasta cooks, place the bacon in a large, cold skillet. Turn the heat to medium and cook, stirring, until crisp and golden, about 7–9 minutes. If using garlic, add it during the last minute to perfume the fat, then remove and discard the garlic clove.

Adjust the fat. You want about 2–3 tablespoons of rendered bacon fat in the pan. If there’s more, spoon off the excess. This keeps the sauce luscious but not greasy.

Combine pasta and bacon. Add the drained pasta to the skillet with the bacon and toss to coat. Turn off the heat and let the pan cool for 30–45 seconds. This step prevents scrambled eggs.

Create the sauce. Pour the egg-cheese mixture over the pasta, tossing quickly and constantly. Add a splash of reserved pasta water—start with 1/4 cup—until the sauce becomes glossy and silky. The residual heat should thicken the sauce without curdling the eggs.

Taste and adjust. Add more black pepper and extra cheese to taste. If the sauce thickens too much, loosen it with another splash of pasta water.

Serve immediately. Top with a sprinkle of parsley (optional), more cheese, and cracked pepper. Eat while it’s hot and creamy.