Bring a pot of salted water to a boil and cook the whole wheat penne according to package directions until al dente.
Reserve 2 tablespoons of the pasta cooking water, then drain the pasta and set it aside.
Season the chicken breast with sea salt and black pepper on both sides.
Heat the olive oil in a large skillet over medium-high heat and sear the chicken until golden and cooked through, about 5-6 minutes per side.
Remove the chicken from the skillet, let it rest for a few minutes, then slice it into bite-sized strips.
In the same skillet, reduce heat to medium and sauté the minced garlic for 1 minute until fragrant.
Add the fresh baby spinach to the skillet and cook until just wilted.
In a small bowl, whisk together the Greek yogurt, parmesan cheese, and reserved pasta water until smooth.
Lower the skillet heat to low, then add the cooked pasta, sliced chicken, and yogurt mixture to the pan.
Toss everything together gently until the pasta is coated in a velvety sauce, then garnish with red pepper flakes and serve.