Toast and Crush Peppercorns: Toast black peppercorns over medium-low heat until fragrant, then let cool and crush to a coarse texture.
Grate Cheeses: Grate parmesan and pecorino cheeses using a microplane for a fine texture.
Prepare Egg Mixture: Combine room temperature whole eggs and yolks in a bowl. Add grated cheeses and mix until smooth. Incorporate some of the toasted and crushed black peppercorns.
Prepare Guanciale: Cut guanciale into thick matchsticks or chunks. Lightly brown in a pan with a little olive oil, then remove from heat.
Cook Pasta: Cook pasta in salted boiling water until al dente. Reserve some pasta water.
Combine Ingredients: In a large bowl (not in the pan), combine the hot drained pasta with the egg and cheese mixture, adding guanciale and its rendered fat. Mix vigorously to create a creamy sauce without scrambling the eggs. If needed, add a little pasta water to adjust the sauce consistency.
Serve: Serve immediately, garnished with additional grated cheese and black pepper to taste.