Bring a large pot of salted water to a boil. Meanwhile, cut guanciale into ¾-inch pieces. Line a plate with paper towels. Combine guanciale and oil in a large nonstick skillet; cook over medium heat, stirring occasionally, until golden and crisp, about 5 minutes. Remove skillet from heat. Using a slotted spoon, transfer guanciale to paper towels to drain. Add onion and chiles to skillet; cook, stirring occasionally, until onion is softened, 5 to 7 minutes.

 

Meanwhile, cook pasta in the boiling water until al dente. Return guanciale to skillet and stir to combine; remove from heat. When pasta is al dente, drain pasta and immediately return to pot. Add guanciale mixture, scraping skillet with a rubber spatula to add all of the pan contents to pot with the pasta. Toss to combine. Add cheese and toss once more. Serve immediately.