1. Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente. Reserve 1/2 cup of pasta water, then drain and set aside.

2. Heat olive oil in a large skillet over medium-high heat. Season chicken with salt and pepper.

3. Add chicken to the skillet in a single layer. Cook 5–7 minutes, turning occasionally, until golden and cooked through. Remove from skillet and set aside.

4. Reduce heat to medium and add garlic to the skillet. Sauté for 30–60 seconds until fragrant, being careful not to burn.

5. Slowly whisk in the milk, scraping up any browned bits from the skillet. Bring to a gentle simmer.

6. Reduce heat to low and stir in Greek yogurt and Parmesan cheese until smooth and melted.

7. Add Italian seasoning, black pepper, and optional red pepper flakes. Adjust seasoning to taste. Add a splash of reserved pasta water if needed to thin the sauce.

8. Return cooked chicken to the skillet. Add spinach, if using, and stir until wilted.

9. Add the drained pasta to the skillet and toss everything together to coat well.

10. Serve immediately, garnished with fresh parsley and extra Parmesan if desired.