1. Boil the pasta in a large pot of salted water over high heat according to package directions. Ladle out 1/2 cup (125 mL) of the pasta water before draining the pasta in a colander.
2. While the pasta is boiling, heat the olive oil in a large sauté pan over medium heat and add the pancetta (or bacon), stirring and cooking until crisp, about 6 minutes. Stir in the garlic and black pepper.
3. Whisk the eggs and cheese in a small bowl and set aside.
4. Add the reserved pasta water to the pan with the pancetta (or bacon) and increase the heat to medium-high to warm through. Add the pasta and peas and toss them with tongs to coat it with the sauce and warm it through. Remove the pan from the heat. Add the egg and cheese mixture and the chives or green onions, tossing the pasta until it’s fully coated (the warm pasta will heat the eggs through and melt the cheese). Season to taste—it may not need added salt, depending on the pancetta/bacon.
4. Serve immediately with extra cheese and black pepper sprinkled on top.