Bring a large pot of salted water to a boil and cook the whole wheat spaghetti until al dente according to package directions.
While the pasta cooks, whisk the whole egg, egg whites, grated Parmesan, and grated Pecorino Romano in a small bowl until the mixture is smooth and combined.
Heat a large skillet over medium heat and sauté the diced pancetta for 5-7 minutes until it becomes golden and crispy.
Carefully reserve 0.25 cup of the starchy pasta cooking water, then drain the spaghetti.
Turn off the heat on the skillet and add the hot pasta directly to the pancetta, tossing well to coat every strand in the rendered fat.
Quickly pour the egg and cheese mixture over the pasta, tossing constantly with tongs to create a creamy, emulsified sauce without scrambling the eggs.
Gradually add a splash of the reserved pasta water as needed to reach a silky, glossy consistency that clings to the noodles.
Season the dish with the freshly cracked black pepper and garnish with chopped fresh parsley before serving immediately.