Should I use whole eggs or only yolks in Spaghetti alla Carbonara?
I've asked this question to many friends of mine from Rome, and they all agree that only yolks should be used. Then I managed to find out the scientific reason behind this.

The real challenge with this recipe, which makes the difference between a perfectly made creamy carbonara and just pasta with omelette, lies in temperature control.

As a matter of fact, the problem of keeping the sauce from getting curdled arises when you mix pasta just taken out from water boiling at 100 °C with egg components that coagulate at a much lower temperature. In particular, as anyone having fried an egg knows, egg white coagulates earlier than yolk (protein coagulation temperatures are approx. 60-62 °C for the former, 68-70 °C for the latter).

This means that egg whites are more susceptible to ruin your carbonara, if you can't manage to rapidly decrease the overall temperature below 60 °C. Since egg whites function is just to provide a more fluid substratum (creaminess and flavour come mostly from yolks), they are usually left out and replaced with starchy pasta water.

So, put yolks only (one per person) in a large bowl and whip them, add pasta al dente without straining it first, using a large fork or kitchen pliers to take it straight from the pot, and then quickly mix them together while adding the remaining ingredients.

In this way, cooking water adhering on pasta surface will provide both the liquid base for the sauce and enough heat to thicken it, while the mixing will disperse the heat in excess.