Step 1

Heat oil in a large skillet over medium-low. Cook guanciale, stirring often, until it starts to brown and crisp, 10–15 minutes; it will shrink dramatically as the fat renders. Transfer to a small bowl with a slotted spoon; reserve skillet (do not wipe out).

Step 2

Meanwhile, cook pasta in a large pot of boiling lightly salted water, stirring occasionally, until pasta is about halfway cooked (not quite al dente); drain, reserving 1 ½ cups pasta cooking liquid.

Step 3

Add ¾ cup pasta cooking liquid to reserved skillet and bring to a gentle boil over medium heat, swirling often to encourage drippings and liquid to emulsify, about 1 minute. Add pasta and cook, tossing often and adding more pasta cooking liquid as needed, until pasta is al dente and a thick, glossy sauce forms, 5–7 minutes (this second cooking is why you undercook the pasta initially).

Step 4

Increase heat to medium-high. Add guanciale, pepper, and two-thirds of Pecorino; toss well to combine and melt cheese. Serve pasta topped with remaining Pecorino.