Bring a large pot of salted water to boil.
Heat olive oil in a large saute pan over medium heat, and add onion. Saute for 2 minutes, add bacon, and cook another 8-10 minutes, until bacon and onion are well-browned. Transfer mixture to a paper towel, and let cool while pasta cooks.
Add pasta to water, and cook according to package directions. Reserve 1/4 cup of pasta water.
While pasta is cooking, whisk together cheese, yolks, sour cream, vinegar and onion mixture. In a separate small bowl, when pasta is nearly done, whisk together a tablespoon of the egg mixture with a tablespoon of pasta water, and pour back into the egg mixture. Whisk remaining 3 tablespoons pasta water into the egg mixture.
Drain pasta, and return it to the pot. Toss with the egg mixture and parsley, and serve immediately.