Bring a large pot of salted water to a boil over high heat.

Whisk together the eggs, yolks, Parmesan, Pecorino, pepper and butter in a bowl until well combined.

Add the pasta to the pot of boiling salt water and cook as label directs. Reserve 1 cup of pasta water then drain pasta.

Meanwhile, cook the pancetta in a large skillet over medium heat, stirring occasionally, until crisp, about 8 minutes. Add the spaghetti and half the reserved water to the skillet and toss to combine.

Add the egg mixture and toss to coat. Cook, tossing continuously to avoid scrambling the eggs, until the sauce is creamy, thinning it with the remaining pasta water if it becomes to thick, about 1 minute.

Divide the pasta among the plates and serve sprinkled with more Parmesan.