When I was 18, I lived in Florence for a school year. That time spent in Italy was pivotal to my view of the world and to my culinary education. There was a small trattoria down the street from the villa where we lived, and a friend and I would go there as often as we could. It was at this trattoria that I first learned about spaghetti carbonara. It was transcendant.
According to Marcella Hazan's The Essentials of Classic Italian Cooking, an Italian food historian alleges that this dish become popularized during World War II when American soldiers would bring local families a gift of bacon and eggs. The Italians - more specifically the Romans - would make a pasta dish with the bacon, eggs, and very few other ingredients. Ms. Hazan's classic recipe calls for pancetta, garlic, wine, olive oil, romano and parmigiano-reggiano cheese, pepper and parsley to be added to the spaghetti and eggs. Often, recipes call for peas which are especially delicious and considered a classic part of the dish.
This is a dish that emphasizes ingredients. Every good recipe for spaghetti carbonara talks about the importance of choosing your bacon carefully, exactly which pasta types to use, and the proper choice of olive oil.
When I returned to the States, I was disappointed time and again by American dishes that would claim to be spaghetti carbonara but would add miscellaneous items. I am a purist when it comes to classic dishes, and I expect restaurants to either abide by the tradition or to make it obvious that the dish is not a traditional rendition: caesar salads should have anchovies but not tomatoes or chicken, macaroni and cheese should be just that , and spaghetti carbonara should have very few ingredients beyond bacon and eggs.