Cut the pancetta or bacon into thin strips.
Put the oil, butter and crushed garlic into a saucepan or small saute pan and turn on the heat to medium-high. When the garlic becomes colored a deep gold, remove and discard it.
Put the pancetta or bacon into the pan and saute until it begins to be crisp at the edges. Add the wine and let it boil away for a minute or two; then turn off the heat.
In a large pot, bring about 4-5 quarts water to a boil. Add about 2-3 T salt, and when the water returns to a boil, put in the spaghetti.
Take the bowl from which you'll be serving the spaghetti later, and into it break the three eggs. Beat them lightly, then mix into them both grated cheeses, a liberal grinding of pepper, and the parsley.
When the spaghetti is tender but firm to the bite, drain it and put it into the serving bowl with the egg-and-cheese mixture. Toss rapidly and thoroughly until it is well-coated.
Reheat the pancetta or bacon quickly over high heat, then pour the entire contents of the pan over the spaghetti. Toss again thoroughly and serve immediately.
* Spaghetti with raw eggs and Italian bacon - While there are innumerable minor variations in the way people make this celebrated Roman dish, there are really only two substantially different schools of thought. One maintains that pancetta, a mild, cured, unsmoked Italian bacon, is the only correct bacon to use. The other school insists on the smoked American variety. Both are good, and both are popular in Italy, but the version I prefer is the one with pancetta. The flavor of smoke is not usually associated with Italian food; certainly hardly ever outside of Alto Adige, a German-speaking region in the North that was once part of Austria. In this dish, I find that smoked bacon adds a sharpness that wearies the palate after the first bite-fulls. Try it both ways and decide for yourself.