Boil spaghetti in salted water until al dente (~11 minutes). Reserve ½ cup of hot pasta water, then drain.
Crisp the Guanciale
Add guanciale to a large skillet over medium heat.
Sear 2–3 minutes per side until deeply golden. Remove from heat and keep 1 tablespoon rendered fat in the pan.
Build the Cream–Yolk Liaison
In a mixing bowl, whisk together egg yolks, Pecorino, heavy cream, and black pepper.
Whisk until smooth, glossy, and slightly thick.
Toss & Emulsify
Add hot pasta to the skillet with 1 tablespoon reserved warm guanciale fat (over medium heat).
Toss to fully coat the pasta.
Stream in half (2 tbsp) of the hot pasta water while tossing. If the sauce looks tight or greasy, add pasta water a tablespoon at a time, tossing between additions, until it looks silky.
Remove from heat and add the cream–yolk liaison, tossing vigorously.
Add additional pasta water as needed until glossy and emulsified.
Fold in crispy guanciale. Adjust pepper and cheese.
To Plate
Twirl pasta into nests.
Spoon any extra sauce over top.
Finish with cracked pepper and Pecorino and microplaned white truffle.
Notes
Storage: keep leftovers in an airtight container in the fridge for up to 2 days. Reheat gently with a splash of water to loosen the sauce; carbonara can turn grainy if microwaved.