Bring a large pot of salted water to a boil and cook the high-protein spaghetti until al dente.
While the pasta cooks, finely dice the pancetta and mince the garlic clove.
In a medium skillet over medium heat, sauté the pancetta until the fat renders and it becomes golden and crispy.
Add the minced garlic to the skillet with the pancetta and cook for 30 seconds until fragrant, then remove from heat.
In a small bowl, whisk together the whole egg, egg whites, and finely grated Pecorino Romano cheese until well combined.
Reserve 0.25 cup of the starchy pasta water, then drain the spaghetti.
Add the hot pasta directly into the skillet with the pancetta and garlic, tossing to coat.
Slowly whisk a tablespoon of the hot pasta water into the egg mixture to temper it, preventing the eggs from scrambling.
Pour the egg and cheese mixture over the pasta while stirring constantly and vigorously, adding more pasta water as needed to create a smooth, creamy sauce.
Season with plenty of freshly cracked black pepper and serve immediately in a warm bowl.