Cook spaghetti in salted boiling water until al dente. Reserve 1 cup pasta water and drain.

In a bowl, combine egg yolks, whole egg, Pecorino, and Parmesan. Mix vigorously to form a smooth paste.

In a cold pan, add diced guanciale or pancetta. Turn heat to medium and cook until crispy and golden. Remove a few spoonfuls of rendered fat and set aside the meat.

Add two spoonfuls of rendered fat and a generous amount of black pepper to the egg/cheese mixture. Stir to combine and loosen with a small splash of pasta water.

Turn off the heat and allow the pan to cool slightly. Add drained spaghetti and egg mixture to the pan.

Quickly toss everything together, adding more pasta water as needed to create a smooth, creamy sauce.

Fold in the cooked pancetta or guanciale, add more cheese and pasta water if needed, and stir until fully incorporated.

Serve immediately topped with additional black pepper and cheese.