Bring a large pot of salted water to a boil and cook the spaghetti according to package directions until al dente.
While the pasta cooks, slice the chicken breast into bite-sized pieces and season with half of the sea salt and black pepper.
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.
Lower the heat to medium and add the minced garlic to the skillet, sautéing for 1 minute until fragrant.
Reserve 2 tablespoons of the pasta cooking water, then drain the spaghetti.
In a small bowl, whisk together the Greek yogurt, parmesan cheese, and the reserved pasta water to create a smooth sauce.
Add the cooked spaghetti and baby spinach to the skillet with the chicken, tossing until the spinach begins to wilt.
Remove the skillet from the heat and stir in the yogurt sauce, remaining salt, and pepper until the noodles are evenly coated.
Garnish with fresh chopped parsley and serve immediately.