Cook the spaghetti in salted boiling water until al dente.
In a large skillet, cook the pancetta over medium heat until crispy.
Add diced chicken to the skillet, cooking until golden and cooked through.
Stir in the minced garlic and cook until fragrant, about 1 minute.
In a bowl, whisk together eggs, grated Pecorino Romano, and a generous amount of black pepper.
Once spaghetti is cooked, drain and immediately add to the skillet with pancetta and chicken.
Remove the skillet from heat, then quickly pour in the egg and cheese mixture, tossing to combine.
Add reserved pasta water as needed to adjust the sauce's consistency, then season with salt and pepper.
Serve immediately, garnished with fresh parsley and extra Pecorino Romano if desired.