Heat the olive oil in a large pot or saucepan on medium and toss in the green onions and sauté until soft.
Toss in the onion slices, garlic, and bacon and cook until the bacon is lightly browned. Remove from heat.
Place egg yolks in a very large bowl for tossing pasta. Stir in Parmesan, cream, and sour cream until smooth.
Bring a large pot of salted water to a boil and add pasta. If pasta is fresh, cook 3-4 minutes until al dente or if it is dried pasta, cook 8-10 minutes.
Add bacon mixture and cooked pasta to the sauce bowl and toss to combine. Season with salt and pepper as desired.
Serve immediately and refrigerate leftovers for up to 3 days.
Notes
Make sure the sauce ingredients are close to room temp so you don't cook the eggs or curdle the dairy.
Leftovers might need a splash of milk to loosen up when heating. Stovetop is best for reheating.