Before draining the pasta, reserve at least 1½ cups of the starchy cooking water.
Make the Egg and Cheese Mixture
While the pasta is cooking, place the egg yolks in a large, heatproof serving bowl. Add the Parmesan, Pecorino Romano, several generous grinds of black pepper and a small amount of freshly grated nutmeg.
Mix the ingredients into a thick paste. Add a few tablespoons of hot pasta water and stir until the mixture becomes smooth and creamy.
Set the bowl briefly over the pot of simmering pasta water, without allowing the bottom of the bowl to touch the water. Stir constantly until the mixture is warm—about 120°F, or 50°C—but not hot enough to cook the yolks. Remove the bowl from the heat.
Finish the Carbonara
Drain the bucatini and immediately add the hot pasta to the egg and cheese mixture. Toss thoroughly so that every strand is coated.
Immediately pour the crisp bacon and its hot rendered fat over the pasta. Toss vigorously. The combined heat of the pasta, bacon and rendered fat will gently thicken the egg yolks and melt the cheese.
Add reserved pasta water a little at a time, tossing after each addition, until the sauce becomes smooth, creamy and glossy. It should cling to the bucatini rather than collect at the bottom of the bowl.
Taste before adding any salt. The bacon and cheeses may provide all the salt the dish needs.
Finish with more freshly ground black pepper and another very light grating of nutmeg. Serve immediately.
Bill’s Notes
Bucatini is especially good here because the sauce clings to its broad exterior and finds its way into the tiny hole running through the center.
The heat is the most important part of the recipe. Too little, and the cheese won’t melt properly. Too much, and the yolks become scrambled eggs. Keep the egg mixture warm rather than hot, and let the freshly cooked pasta and rendered bacon fat finish the job.
Always reserve more pasta water than you think you will need. The starch in it loosens the sauce while helping it stay attached to the pasta. It is the ingredient that can turn a heavy mixture of eggs and cheese into a silky carbonara.
And don’t add cream. It doesn’t need it.