Bring a large pot of water to a boil for the pasta.
Shuck corn and trim the bottom of the ears. Set a small bowl upside down in a large bowl, balance each ear of corn on the smaller bowl for stability and scrape the kernels and milk off the cob with sharp knife; the larger bowl will catch the kernels.
Heat a large skillet over medium-high heat with EVOO, 2 turns of the pan. When the oil is hot, add the pancetta or bacon and season with a little coarse black pepper. Render to golden brown, remove to plate with a slotted spoon. Return pan to heat and melt butter. Add corn, season with salt and red chili flakes, and lightly brown and caramelize, 5-6 minutes.
Salt pasta water and drop pasta.
Add garlic and whites of onions to corn and stir a minute or 2.
In a bowl, whisk up the egg yolks. Slowly whisk in a full cup of hot, starchy boiling water to temper the yolks; whisk in cheese.
Drain pasta and toss with corn, reserved pancetta or bacon and parsley. Top with scallion greens and serve.