Bring a large pot of well salted water to a boil over medium heat.
Add about 2 tablespoons olive oil to a large skillet over medium heat. Add the pancetta a medium heat and cook until it starts to color and become crisp. Turn off the heat and reserve.
Drop the pasta into the salted boiling water and cook it 1 minute less than it says on the package, usually about 6 to 7 minutes. Bite the pasta to check the consistency.
While the pasta is cooking, crack the eggs into a large mixing bowl. Add the grated cheeses and season with salt. Whisk vigorously until it becomes a homogenous. Season generously with black pepper.
When the pasta is just about done, return the pan with the pancetta to medium heat. Remove the pasta from the cooking water. Toss or stir the pasta into the pancetta to coat the pasta with the remaining fat in the skillet. Immediately vigorously stir the egg mixture into the pasta. Cook for 1 to 2 minutes, stirring constantly until the egg mixture looks like a cream sauce.
Serve immediately garnished with sliced scallions.