This is a simple dish with few ingredients, but the preparation can be a little fussy. Timing is critical - it's the kind of thing you want to have everything prepped and ready to go for before starting.
Here are the ingredients: spaghetti, eggs, parmesan cheese, and bacon. Pancetta is of course the traditional meat component, but I like the smokiness of good American bacon. And use a high-quality pasta - this is a very nice spaghetti alla chitarra I found locally.
Yes, I weigh my pasta. I'm weird like that.
Here's the prep work (almost) completed. I don't beat the egg till the pasta is almost done - the first time I had this, in a restaurant, it was served with just the egg yolk in half a shell, the idea being that I would mix it into the dish to finish the sauce. I certainly don't mind doing that, but it's easier to just do it in the kitchen.
Figure on one whole egg and half a cup of grated parmesan per half-pound of pasta. I've also added a little chopped parsley here.
Fry the bacon gently in a large sauté pan. If it renders a lot of grease, you can pour some of it off, but you do want some. I tend to leave about a tablespoon or two. Start the pasta when the bacon is about half done.
When it gets nice and crispy like this, just keep it warm while you finish boiling the pasta. Beat the egg(s) when the pasta is about a minute or two from completion.
When the pasta is done, dump it into the pan with just a little pasta water - I have about 1/4 cup here, I think. Stir it up really well, and...
.. stir in the egg very quickly, while the pasta is still really hot. You want to cook the egg without letting it curdle, so don't let the egg pool in the pan.
Finally, stir in the cheese. Keep moving the pasta around until all of the cheese melts. Add a little more pasta water if the sauce needs to be loosened up a bit. If you're adding parsley (as I am here), stir it in right at the end.
And here it is plated, with a nice green salad. This is a really rich and satisfying dish, and kind of a nice break from the heavier tomato- or cream-based sauces we Americans tend to take our pasta with.