Bring a large pot of salted water to a boil. Add whole wheat pasta and cook according to package instructions until al dente. Before draining, save about 1/4 cup of the pasta water. Drain and set aside.

While the pasta cooks, heat 1 tablespoon of olive oil over medium heat in a large nonstick skillet. Add cubed chicken breast, then season with salt, pepper, paprika, and Italian seasoning. Cook the chicken for about 5-6 minutes, flip occasionally, until golden on the outside and cooked through. Transfer the chicken to a plate and set aside.

In the same skillet, add the remaining tablespoon of olive oil. Stir in the minced garlic and sauté for 30-60 seconds, until fragrant. Don't let it brown. Next, sprinkle in the whole wheat flour and stir to form a light roux. Cook for about 30 seconds.

Slowly pour in the chicken broth while whisking constantly to avoid lumps. Add the milk and continue whisking until the sauce begins to thicken—this should take 2-3 minutes.

Reduce the heat to low and stir in the Greek yogurt. Mix well until fully incorporated. Add the grated Parmesan cheese and stir until it melts into the sauce. If the sauce feels too thick, add a splash of reserved pasta water until it reaches desired consistency.

Return the cooked chicken to the skillet along with any juices. Toss in the cooked pasta and add the spinach if using. Stir everything together until the pasta and chicken are fully coated in the creamy sauce and the spinach is just wilted.

Divide the pasta among plates and garnish with chopped parsley and a sprinkle of extra Parmesan. Serve immediately for the best flavor and texture.