Step 1

In a large pot, bring 4 quarts of water to a boil. Meanwhile, in a 10-inch skillet over medium, cook the pancetta until crisp, about 5 minutes. Using a slotted spoon, transfer the pancetta to a paper towel–lined plate; reserve 2 tablespoons of the rendered fat.

Step 2

In a large saucepan, whisk the water and cornstarch until smooth. Add the pecorino and stir until evenly moistened. Set the pan over medium-low and cook, whisking constantly, until the cheese melts and the mixture comes to a gentle simmer and thickens slightly, about 5 minutes. Remove from the heat, whisk in reserved pancetta fat and set aside.

Step 3

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.

Step 4

Pour the pecorino mixture over the pasta and toss with tongs until combined, then toss in the pepper and crisped pancetta. Let stand, tossing two or three times, until most of the liquid has been absorbed, about 3 minutes. The pasta should be creamy but not loose. If needed, toss in reserved pasta water 1 tablespoon at a time to adjust the consistency. Transfer to a warmed serving bowl and serve, passing more pecorino and pepper on the side.