Bring a pot of salted water to a boil and cook the whole wheat penne according to package directions until al dente.
Before draining the pasta, carefully reserve 2 tablespoons of the starchy pasta water and set aside.
While the pasta cooks, season the chicken breast with sea salt, black pepper, and dried oregano.
Heat the olive oil in a large skillet over medium-high heat and sear the chicken until golden brown and cooked through, about 5-6 minutes per side.
Remove the chicken from the skillet, let it rest for 2 minutes, then slice into bite-sized strips.
In the same skillet, reduce heat to medium and add the minced garlic, sautéing for 1 minute until fragrant.
Stir in the baby spinach and cook until just wilted.
Whisk together the Greek yogurt, grated parmesan, and reserved pasta water in a small bowl to create a smooth sauce base.
Add the cooked pasta and sliced chicken back into the skillet with the spinach.
Pour the yogurt sauce over the mixture and toss everything together over low heat until the sauce is creamy and coats the pasta evenly.