Bring a pot of salted water to a boil and cook the whole wheat spaghetti until al dente, reserving 0.25 cup of pasta water before draining.
While the pasta cooks, dice the chicken breast into small bite-sized pieces and season with sea salt.
In a large skillet over medium heat, cook the diced pancetta until the fat has rendered and it becomes crispy.
Add the diced chicken to the skillet with the pancetta and sauté until the chicken is golden brown and cooked through.
In a small bowl, whisk together the egg, grated parmesan cheese, and black pepper until well combined.
Add the cooked pasta and baby spinach to the skillet with the chicken and pancetta, tossing for 1 minute until the spinach begins to wilt.
Remove the skillet from the heat entirely to prevent the eggs from scrambling.
Pour the egg and cheese mixture over the pasta, adding a splash of the reserved pasta water, and toss vigorously until a creamy, glossy sauce forms and coats every strand.