Bring a large pot of salted water to a boil and cook the spaghetti according to package directions until al dente.
While pasta cooks, reserve 0.25 cup of the starchy pasta water, then drain the noodles.
In a large skillet over medium heat, add the diced pancetta and cook until crispy, about 5 minutes; remove with a slotted spoon and set aside.
Season the chicken breast with half of the salt and pepper, then add it to the same skillet with olive oil and cook until golden and cooked through, about 6-7 minutes per side.
Remove the chicken, let it rest for 2 minutes, then slice into thin strips.
In the same skillet, sauté the minced garlic for 30 seconds until fragrant, then add the fresh spinach and cook until just wilted.
In a small bowl, whisk together the Greek yogurt, parmesan cheese, and the reserved pasta water until smooth.
Reduce the skillet heat to low, return the spaghetti, chicken, and pancetta to the pan.
Pour the yogurt mixture over the pasta and toss everything together until creamy and well-coated.
Garnish with fresh parsley and the remaining salt and pepper before serving immediately.