Bring a large pot of salted water to a boil. Cook guanciale in a cold skillet over medium heat until crisp, about 8 to 10 minutes. Remove guanciale with a slotted spoon and set aside, leaving the fat in the pan. Remove skillet from heat.

Whisk the egg yolks, whole egg, 1 cup pecorino, and 1 tsp black pepper in a bowl until smooth.

Boil spaghetti until al dente, about 10 to 11 minutes. Reserve 1½ cups pasta water, then transfer the drained pasta directly to the skillet with the guanciale fat. Toss over very low heat until coated.

Remove the skillet from heat. Pour the egg mixture over the pasta and toss vigorously, drizzling in reserved pasta water a little at a time until a glossy sauce forms. Fold in the crispy guanciale, then serve in warm bowls with more pecorino and black pepper.