Bring a pot of salted water to a boil and cook the whole wheat penne according to package directions until al dente.
While the pasta cooks, cut the chicken breast into bite-sized pieces and season with sea salt and black pepper.
Heat the olive oil in a large skillet over medium heat and sauté the chicken until golden and cooked through, about 5-7 minutes.
Add the minced garlic and halved cherry tomatoes to the skillet, cooking for 2 minutes until the tomatoes begin to soften and release their juices.
Stir in the baby spinach and cook just until wilted, then remove the skillet from the heat.
In a small bowl, whisk together the basil pesto and Greek yogurt until smooth.
Drain the pasta, reserving two tablespoons of pasta water, and add the pasta to the skillet with the chicken and vegetables.
Pour the creamy pesto sauce over the mixture, add the reserved pasta water, and toss everything together until the pasta is well coated and the sauce is silky.