In a mixing bowl, whisk together eggs, egg yolk, chili crisp, soy sauce, sugar, and sesame oil until smooth.
Set aside.
Cook the Pasta
Bring a pot of salted water to a boil.
Cook spaghetti until just al dente.
Reserve at least 1 cup of hot pasta water, then drain the pasta.
Render the Bacon
Heat a large skillet over medium heat.
Add the bacon and cook until the fat renders and the pieces are crisp.
Add green onion whites and cook for 30–45 seconds until fragrant.
Clear the Pan
Remove the bacon and scallions from the skillet, leaving the rendered fat behind. Remove pan from the heat.
Build the Sauce in the Pan
While the pan is still hot (but off of the heat), add about 3 tablespoons of hot pasta water to the skillet.
Slowly pour in the sauce, a few tablespoons at a time, while stirring constantly. The key is to let the sauce mix in to the rendered fat and pasta water without overcooking or scrambling. If you see the egg starting to scramble, continue to stir but wait for the pan to cool down a bit more before continuing.
Finish
Add the bacon and scallion whites back to the pan and toss.
Finish with scallion greens, extra chili crisp, and black pepper if desired.
Notes
Hot pasta water is essential for a smooth emulsion—do not let it cool.
Stir constantly when adding the egg mixture to prevent curdling.
The sauce should look loose in the pan and will tighten quickly once plated.