1. Bring a large pot of well-salted water to a boil for the pasta.

2. Heat a deep skillet over medium-high heat and lightly coat with cooking spray or oil.

3. Season the chicken with salt and black pepper, then add it to the hot pan. Cook for 3–4 minutes per side until lightly golden. Remove the chicken and set aside.

4. Lightly coat the pan again if needed. Add the garlic and cook gently for 1–2 minutes until fragrant, stirring constantly so it does not brown.

5. Pour in about 1/2 cup of the chicken stock and let it simmer briefly, loosening any flavorful bits from the pan.

6. Cook the penne in the boiling water until al dente. Before draining, reserve about 1/3 cup of the pasta water. Drain and set aside.

7. Add the remaining chicken stock, milk, and cream cheese to the skillet. Simmer over medium heat, whisking gently until the cream cheese melts and the sauce is smooth.

8. In a small bowl, mix the cornstarch with a splash of cold water to form a slurry. Stir it into the sauce and simmer until slightly thickened.

9. Return the chicken to the pan along with the spinach. Cook for a few minutes until the spinach wilts and the chicken is fully cooked through.

10. Add the cooked pasta, reserved pasta water, and grated cheese. Stir until everything is well coated and the cheese melts into the sauce.

11. Taste and adjust seasoning with additional salt and black pepper as needed.

12. Serve warm and enjoy.