Bring a large pot of salted water to a boil and cook the whole wheat spaghetti according to package directions until al dente.
While the pasta cooks, dice the chicken breast into bite-sized pieces and season with a pinch of salt and pepper.
Heat olive oil in a large skillet over medium heat; add the pancetta and cook until crispy, then remove and set aside on a paper towel.
In the same skillet, add the chicken pieces and sauté until golden brown and cooked through, approximately 5-7 minutes.
In a small bowl, whisk together the egg, grated parmesan cheese, and black pepper until well combined.
Reserve 0.25 cup of the starchy pasta water, then drain the spaghetti.
Turn off the heat in the skillet with the chicken. Add the hot pasta and crispy pancetta to the pan, tossing to combine.
Slowly pour the egg mixture over the pasta while tossing constantly; the residual heat will create a creamy sauce without scrambling the eggs.
Add a splash of the reserved pasta water if needed to reach your desired consistency, then garnish with fresh parsley and serve immediately.