Step 1

Bring a large pot of water to a boil over high heat. Salt the water (use slightly less than you might for other pastas, as the cheese and pork add quite a bit of salinity to the dish).

Step 2

Place a large sauté pan over low heat. Add the guanciale and cook slowly until the fat has rendered and the meat parts start to get crispy, 5 to 7 minutes. Line a plate with paper towels. Using a slotted spoon, transfer the crisped guanciale to the paper towels to drain. Reserve 1/4 cup of the rendered fat.

Step 3

Add the egg yolks to a large bowl. Use a spoon or spatula to stir them into a smooth liquid. Do not whip them. Add the Parmigiano and 3/4 cup of the Pecorino and stir to make a paste. Slowly stir in the reserved rendered fat. Add a hefty amount (about 40 grinds) of pepper and half of the reserved guanciale. Stir to combine.

Step 4

Add the spaghetti to the water and cook for 5 to 8 minutes, until al dente.

Step 5

Add 2 ladles (1/2 cup) pasta cooking water to the bowl in a slow, steady stream while stirring. This will further temper the eggs so they don't curdle and will also loosen the mixture to form your sauce.

Step 6

Using tongs or a pasta basket, remove the spaghetti from the pot and transfer to the bowl. Quickly but gently toss the pasta and cheese-egg yolk paste. As the sauce tightens, continue to add pasta cooking water a splash at a time until you have a smooth, silky sauce coating the pasta.

Step 7

Divide into bowls and garnish with the remaining Pecorino, the reserved guanciale and with pepper to taste.