Bring a large pot of water to a boil, add sea salt, and cook the whole wheat spaghetti according to package directions until al dente.
While the pasta cooks, dice the pancetta and chicken breast into bite-sized pieces.
In a large skillet over medium heat, sauté the pancetta until the fat renders and it becomes crispy, then remove with a slotted spoon and drain on a paper towel.
In the same skillet, add the chicken breast and minced garlic, cooking until the chicken is golden brown and cooked through.
In a small bowl, whisk together the large egg, Pecorino Romano cheese, and black pepper until well combined.
Reserve 0.25 cup of the starchy pasta water, then drain the spaghetti and add it directly to the skillet with the chicken and baby spinach.
Remove the skillet from the heat immediately to prevent the eggs from scrambling.
Pour the egg mixture over the pasta, adding the reserved pasta water a tablespoon at a time while tossing vigorously until a smooth, creamy sauce forms.
Fold in the crispy pancetta and serve immediately while hot.