In a 10-inch skillet over medium, cook the pancetta, stirring, until crisp, about 5 minutes. Using a slotted spoon, transfer to a paper towel–lined plate.

Measure out and reserve 3 tablespoons of the rendered fat; if needed, supplement with olive oil. Set the pancetta and fat aside.

In a large pot, bring 4 quarts water to a boil. Meanwhile, in a large saucepan, whisk the water, egg yolks and cornstarch until smooth. Add the cheese and stir until evenly moistened.

Set the pan over medium-low and cook, whisking constantly, until the mixture comes to a gentle simmer and is airy and thickened, 5 to 7 minutes; use a silicone spatula to occasionally get into the corners of the pan.

Off heat, whisk in the reserved pancetta fat. Remove from the heat and set aside.

Stir the pasta and salt into the boiling water and cook until al dente. Reserve about ½ cup of the cooking water, then drain the pasta very well. Return the pasta to the pot and let cool for about 1 minute.

Pour the pecorino-egg mixture over the pasta and toss with tongs until well combined, then toss in the pepper. Let stand, tossing the pasta two or three times, until most of the liquid has been absorbed, about 3 minutes.

Crumble in the pancetta, then toss again. The pasta should be creamy but not loose. If needed, toss in up to 2 tablespoons reserved pasta water to adjust the consistency. Transfer to a warmed serving bowl and serve, passing more pecorino and pepper on the side.