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 to 1/2 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 for 5 to 6 minutes, flipping occasionally, until golden on the outside and cooked through (internal temperature 165°F). Transfer the chicken to a plate and cover loosely with foil to keep warm.

In the same skillet over medium heat, add the remaining tablespoon of olive oil. Stir in the minced garlic and sauté for 30 to 60 seconds, until fragrant but not browned. Sprinkle in the whole wheat flour and stir into the garlic oil 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 and coats the back of a spoon, about 2 to 3 minutes.

Reduce the heat to low to prevent curdling, then stir in the room-temperature 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 or two of your reserved pasta water until it reaches your 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 wilts slightly, about 1 to 2 minutes.

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