Whisk together the eggs, heavy cream, and parmesan cheese.
Set the mixture aside.
Boil your noodles, drain, and toss them with a bit of oil or butter to keep them from sticking.
Meanwhile, in a large skillet, fry the onion in butter until totally soft.
Typically, the onion in this pasta dish doesn't take on color.
Be sure to adjust the heat lower so that the onion doesn't take on color as it cooks.
Add in the proscuitto and heat it for a few moments until fragrant.
Toss hot, drained noodles and turn off the heat.
Dump the egg mixture onto the hot noodles and toss thoroughly with fresh cracked pepper (or you can let your guests add their own). As you stir the ingredients together, the eggs will thicken and the cheese will melt, all thanks to the residual heat of the pasta.
Be sure to add a lot of pepper. That's half the fun of papalina.