Boil a pot of salted water and cook the spaghetti until al dente, reserving 1/4 cup of pasta water before draining.
While the pasta cooks, heat the olive oil in a large pan over medium heat and sauté the diced chicken breast until golden and cooked through.
Add the pancetta to the pan with the chicken and continue cooking until the pancetta is crispy and fragrant.
In a small bowl, whisk together the egg, grated parmesan cheese, and black pepper until the mixture is smooth.
Add the minced garlic to the pan with the meat and sauté for 30 seconds until aromatic.
Turn off the heat entirely and add the cooked pasta to the pan, tossing it thoroughly with the chicken and pancetta.
Slowly pour the egg and cheese mixture over the pasta while tossing constantly, adding the reserved pasta water one tablespoon at a time to create a silky sauce.
Garnish the carbonara with fresh parsley and serve immediately while hot.