Preheat oven to 400°F (200°C) and spray a baking dish with nonstick spray.

Season chicken breasts with salt and pepper on both sides.

In a skillet over medium heat, heat olive oil. Sauté onion until translucent (about 4-5 minutes), then add garlic for another minute.

Stir in spinach until wilted (about 2 minutes).

Lower heat and mix in cream cheese until melted; add chicken broth and stir until smooth. Gradually add Parmesan cheese and simmer until thickened.

Nestle seasoned chicken into the sauce, then transfer to the oven. Bake for 25-30 minutes or until chicken reaches an internal temperature of 165°F (75°C).