In a deep pot boil water, add enough salt so the water is salty like the sea! While the water comes to a boil, in a small bowl whisk egg yolks and whole egg together and set aside. Roughly chop parsley and set aside. Cut pancetta into a medium dice and set aside.
Once water is boiling add pasta. Cook until al dente -- usually 1 to 2 minutes less than the recommended cooking time on the package. While the pasta is cooking, in a separate shallow pot add olive oil, turning the pot so the oil will coat everywhere. Once hot (oil should appear shiny but not quite smoking), add pancetta and stir occasionally until golden brown. When the pancetta is golden brown, add garlic and onions and cook until the onions become translucent.
Once the pasta is cooked, drain (reserve 1 cup of pasta water). Add pasta into the onion mixture and stir until mixed evenly. Add parsley, season with salt and black pepper, and again mix thoroughly.
Turn the heat off before the next step. In one hand stir continuously while pouring eggs in a steady stream into the sauce. Make sure the heat is off so eggs do not scramble. Lastly add parmesan and stir.
Taste and season with salt, parmesan and black pepper depending on preference. If the sauce is too thick add a bit of pasta water to thin it out.