While a large pot of lightly salted water begins to boil for the pasta, put the bacon and butter in a large skillet and cook over medium heat. You could omit the butter but for traditional carbonara just...don't do it. Butter is good.
As soon as the water is ready, cook pasta according to directions on package.
Once the bacon starts to get brown and crispy, add the garlic into the skillet and cook for another few minutes. Remove from heat. (drain some of the fat if desired but reserve at least ~3 tablespoons in the pan).
Beat your eggs and set aside for a bit later.
Saving 1/4 cup of the water from the pasta, drain the rest.
Add the pasta to the pan with the bacon and garlic and toss well so that it is thoroughly mixed together.
Let the 1/4 cup of water cool for a few minutes and then mix it into the beaten eggs.
Add egg mixture to the skillet with the pasta, toss, add cheeses, and toss some more until everything is well mixed together.
Sprinkle with a bit more cheese, some black pepper, and fresh parsley and ENJOY!