Like most good things, carbonara is simple but requires la practica, which I don't say to be off-putting—simply honest. Having written this, you will now of course go off and make the perfect carbonara on your first attempt and wonder what on Earth I was going on about. Good for you.
The goal for carbonara is one in which the cured pork and its fat, plus beaten eggs, grated cheese, and a hearty slosh of starchy pasta cooking water come together to form a soft yellow cream on the strands of spaghetti or rigatoni.
The way to get there is to understand what happens and when: that if you put drained pasta into a pan with hot pork fat at the right moment, add beaten eggs and grated cheese and enough pasta cooking water, then pull the hot pan from the heat and stir purposefully, you should get a creamy sauce that clings to each tube.
Having understood this, you'll also understand the need for practice. It can't possibly be any other way. Through practice, you will notice how the cured pork renders and how much fat there is, which will, of course, be different for every piece of pork and stove. Practice will help you find the best arrangement of frying pan, pasta pan, and vessel (cup) for the reserved cooking water so as to make the sequence as easy as possible.
But most of all, practice helps you become familiar with the sequence of movements. Here's what I have been taught here in Rome (where there are, of course, as many recipes and secrets as there are Carbonara cooks). Think of it as a template to try, practice, and make your own. Read this carefully before you start.
First, cut 150 grams cured pork into short, thick strips. In Rome, Guanciale (cured pigs cheek) is traditionally used for Carbonara: Purists claim it is indispensable. That said, quite a few Romans I know prefer pancetta. If you can't find either, bacon works, too.
Bring a large pan of water to a rolling boil. Fry pork in a little olive oil until the fat renders and the pieces are golden. Remove the pan from the heat.
Now, salt the boiling water, stir, add 450 grams pasta, and cook until al dente, which means to the tooth— so firm. Check the pasta packet and start tasting at least two minutes before the end of the recommended cooking time.
While the pasta is cooking, gather your sauce ingredients: 2 large eggs, 2 egg yolks, 80 grams cheese, and salt. As for cheese, the distinctive sheep's milk pecorino Romano, with its salty and piquant punch, is ideal. (But Parmesan works, too, as will a mixture of the two.)
Beat together the eggs, yolks, cheese, and tiny pinch of salt (the salt in the pasta water and cheese has this mostly covered) and whisk. When the pasta is nearly ready, heat up the meat pan again, remove most of the strips of meat to a warm plate; the fat should be hot.
Remove a cupful of pasta cooking water, then drain the pasta, tip it into the hot pan with the pork fat, and stir. Pull the pan from the flame and add the egg mixture, plus a good slosh of pasta cooking water.
Stir and swish vigorously until you have a golden cream. You are watching for the moment when the considerable heat of the rendered fat and your stirring thickens the egg—kept creamy by the starchy water—and transforms into a soft, batter-like sauce that clings to the pasta but still lets everything slide seductively. Eureka.
Add reserved pork and stir again. If it seems to dry or clumpy, add a bit more cooking water and stir again. Divide between plates and serve immediately.
As my Roman neighbor once said, practice may also let you scramble or flood, which is frustrating but still edible, and how else will our hands and hearts learn?
What do you put in your carbonara, traditional or not? Drop your ideas right into the comments.